Unified query converter for Visibility

[rodrigozhou]

What changed?

Unify Visibility query converters.

The new query converter is the struct query.QueryConverter[ExprT]. The generic parameter specify the output type of the converter (in ES is elastic.Query, in SQL is sqlparser.Expr).

The query converter has a query.StoreQueryConverter[ExprT]. This is the Visibility store specific implementation for building the output query.

For example, the store needs to implement BuildAndExpr(exprs) to tell the query converter how to build the AND expression. In SQL, it's *sqlparser.AndExpr{exprs}. In Elasticsearch, it's elastic.NewBoolQuery().Filter(exprs).

The store query converter for SQL needs a plugin query converter called sqlplugin.VisibilityQueryConverter which is implemented by each plugin (MySQL, PostgreSQL, SQLite). This interface is needed to build DB specific syntax for KeywordList and Text searches as well as to build the final SELECT statements.

Added dynamic config system.VisibilityEnableUnifiedQueryConverter that acts as switch between the legacy and the unified query converters.

Why?

There are two query converters: one for Elasticsearch, and another for SQL.
They are somewhat similar, and have quite a few code duplications for validation, modifying the query, etc.
Unifying the query converter ensures that we provide the exact same behavior across different Visibility stores.

How did you test it?

• built
• run locally and tested manually
• covered by existing tests
• added new unit test(s)
• added new functional test(s)

I've added a lot of unit tests for the new code with coverage close to 100%.

Note that there has been basically no changes to functional tests, which suggests that the change works well.

Potential risks

There might be some edge cases that either query converters that this unified query converter might deal differently.