Explicitly support connection adapters

[scarroll32]

Ransack should explicitly support Rails connection adapters, and these should be documented and supported with specs / CI.

Rails 7.1+ / 8.x

• postgresql in active_record/connection_adapters/postgresql_adapter.rb
• mysql2 in active_record/connection_adapters/mysql2_adapter.rb
• trilogy in active_record/connection_adapters/trilogy_adapter.rb, uses mysql as the backend
• sqlite3in active_record/connection_adapters/sqlite3_adapter.rb

Third-Party Extensions

These are not supported by the Ransack gem explicitly but are known to be generally compatible. Enhancements to Ransack to support these should be generalisable or else applied in the adapter gem.

• oracle_enhancedprovided by the activerecord-oracle_enhanced-adapter gem.
• sqlserver provided by the activerecord-sqlserver-adapter gem.

Support for PostGIS

As noted in this open issue features from PostGIS are not supported, but it has been added to the codebase and CI as if the activerecord-postgis-adapter gem is added to a project, it overrides the extension name to PostGIS.

Some options are to change the else clause in this code to default to Postgres (hacky) or better to explicitly add all supported connection adapters by name and then allow an override with a Ransack config setting (preferred).

[gregmolnar]

Do we really need to worry about the Active Record connection adapter? Ransack should just work with Active Record, regardless of the connection adapter IMHO.