unindexed_foreign_keys validation for composite primary key on HABTM

[benaitcheson]

Fix false positive for HABTM tables with composite primary keys

Problem

The UnindexedForeignKeys detector currently reports false positives for HABTM
(Has And Belongs To Many) tables that use composite primary keys. It suggests
adding indexes that already exist as part of the primary key.

Solution

Modified the indexed? method to recognize columns that are part of composite
primary keys. This prevents false positives while maintaining the original
functionality for single-column indexes.

Example

Given a HABTM table:

CREATE TABLE companies_users (
  company_id bigint NOT NULL,
  user_id bigint NOT NULL,
  PRIMARY KEY (company_id, user_id)
);

Testing

Pointed the repo at this branch and ran the UnindexedForeignKeys command. Has fixed the issue for my repo.

[fatkodima]

I think this will be fixed as part of #148.

[benaitcheson]

I think this will be fixed as part of #148.

Amazing! Thanks @fatkodima. Love your work.