management/security-realm/authentication/users has required "value" attribute, but there is now credential-reference too and there is no way how to update existing resource to use another option.

[standalone@localhost:9990 /] /core-service=management/security-realm=ManagementRealm/authentication=properties:remove()
[standalone@localhost:9990 /] /core-service=management/security-realm=ManagementRealm/authentication=users:add()

[standalone@localhost:9990 /] /core-service=management/security-realm=ManagementRealm/authentication=users/user=pepa:add(password=testpassword)
{"outcome" => "success"}

[standalone@localhost:9990 /] /core-service=management/security-realm=ManagementRealm/authentication=users/user=pepa:undefine-attribute(name=password)
{
    "outcome" => "failed",
    "failure-description" => "WFLYCTL0172: password is required",
    "rolled-back" => true
}
[standalone@localhost:9990 /] /core-service=management/security-realm=ManagementRealm/authentication=users/user=pepa:write-attribute(name=credential-reference, value={clear-text=password123})
{
    "outcome" => "failed",
    "failure-description" => "WFLYCTL0105: password is invalid in combination with credential-reference",
    "rolled-back" => true
}

[standalone@localhost:9990 /] /core-service=management/security-realm=ManagementRealm/authentication=users:read-resource-description
{
    "outcome" => "success",
    "result" => {
        "description" => "Configuration to use a list users stored directly within the standalone.xml or host.xml configuration file as the user repository.",
        "deprecated" => {
            "since" => "1.7.0",
            "reason" => "The security-realm configuration is deprecated and may be removed or moved in future versions."
        },
        "access-constraints" => {"sensitive" => {"security-realm" => {"type" => "core"}}},
        "attributes" => {},
        "operations" => undefined,
        "notifications" => undefined,
        "children" => {"user" => {
            "description" => "An authorized user.",
            "model-description" => undefined
        }}
    }
}
[standalone@localhost:9990 /] /core-service=management/security-realm=ManagementRealm/authentication=users:read-resource-description(recursive=true
{
    "outcome" => "success",
    "result" => {
        "description" => "Configuration to use a list users stored directly within the standalone.xml or host.xml configuration file as the user repository.",
        "deprecated" => {
            "since" => "1.7.0",
            "reason" => "The security-realm configuration is deprecated and may be removed or moved in future versions."
        },
        "access-constraints" => {"sensitive" => {"security-realm" => {"type" => "core"}}},
        "attributes" => {},
        "operations" => undefined,
        "notifications" => undefined,
        "children" => {"user" => {
            "description" => "An authorized user.",
            "model-description" => {"*" => {
                "description" => "An authorized user.",
                "deprecated" => {
                    "since" => "1.7.0",
                    "reason" => "The security-realm configuration is deprecated and may be removed or moved in future versions."
                },
                "access-constraints" => {"sensitive" => {"security-realm" => {"type" => "core"}}},
                "attributes" => {
                    "credential-reference" => {
                        "type" => OBJECT,
                        "description" => "The reference to credential for the password stored in CredentialStore under defined alias or clear text password.",
                        "expressions-allowed" => false,
                        "required" => false,
                        "nillable" => true,
                        "alternatives" => ["value"],
                        "access-constraints" => {"sensitive" => {"credential" => {"type" => "core"}}},
                        "value-type" => {
                            "store" => {
                                "type" => STRING,
                                "description" => "The name of the credential store holding the alias to credential.",
                                "expressions-allowed" => false,
                                "required" => false,
                                "nillable" => true,
                                "alternatives" => ["clear-text"],
                                "requires" => ["alias"],
                                "min-length" => 1L,
                                "max-length" => 2147483647L
                            },
                            "alias" => {
                                "type" => STRING,
                                "description" => "The alias which denotes stored secret or credential in the store.",
                                "expressions-allowed" => true,
                                "required" => false,
                                "nillable" => true,
                                "requires" => ["store"],
                                "min-length" => 1L,
                                "max-length" => 2147483647L
                            },
                            "type" => {
                                "type" => STRING,
                                "description" => "The type of credential this reference is denoting.",
                                "expressions-allowed" => true,
                                "required" => false,
                                "nillable" => true,
                                "min-length" => 1L,
                                "max-length" => 2147483647L
                            },
                            "clear-text" => {
                                "type" => STRING,
                                "description" => "Secret specified using clear text. Check credential store way of supplying credential/secrets to services.",
                                "expressions-allowed" => true,
                                "required" => false,
                                "nillable" => true,
                                "alternatives" => ["store"],
                                "min-length" => 1L,
                                "max-length" => 2147483647L
                            }
                        },
                        "access-type" => "read-write",
                        "storage" => "configuration",
                        "restart-required" => "no-services"
                    },
                    "password" => {
                        "type" => STRING,
                        "description" => "The user's password.",
                        "expressions-allowed" => true,
                        "required" => true,
                        "nillable" => true,
                        "alternatives" => ["credential-reference"],
                        "min-length" => 1L,
                        "max-length" => 2147483647L,
                        "access-type" => "read-write",
                        "storage" => "configuration",
                        "restart-required" => "no-services"
                    }
                },
                "operations" => undefined,
                "notifications" => undefined,
                "children" => {}
            }}
        }}
    }
}