Add simple row based security to data roles

A common request is to implement row based security. The common workaround of modifying transformations is generally not a good solution.

We should look at adding support for simple table filters and column masks.

To be effective, filtering permissions however would have to act differently than normal data roles. They would need to be applied all the time - and not just against the end user queries.

For example, for tables:

<permission>
<resource-name>SCHEMA.TABLE</resource-name>
<filter>COLUMNA=2</filter>
</permission>

Meaning allow the CRUD of the given row only if COLUMNA has the value of 2. Any valid predicate against just the referenced table would be allowed as a filter. Each such permission would be applied as an additional predicate any time the table is referenced (in views, inserts, updates, deletes, etc.).

Allows would not be specified here as we want the filter to always specify inclusion. Any applicable permissions in additional roles would be applied disjunctively - filter OR filter.

We could possibly support column masks via case expressions, such as:

<permission>
<resource-name>SCHEMA.TABLE.COLUMN</resource-name>
<mask>CASE WHEN ...</mask>
</permission>

However this is slightly more complicated. Presumably the mask would only apply to projection and makes more sense to be applied at the final output/user query (more like a data role).

If we work the issue to specify the object type of a permission, then the name could alternatively refer to datatype or even an extension property to make the masking a little easier.