Migrate RuboCop cops to Base API

[evgeny-matveev]

Hi everyone,

This PR closes #71

The main goal was pretty simple — those deprecation warnings were starting to drive me a bit crazy, so I decided to clean them up once and for all 🙂 I tried to keep the changes as small and straightforward as possible — didn't want to overcomplicate things or touch unrelated parts of the codebase.

Let me know if I missed something or if there's a better way to handle any of these.
Thanks for taking a look! 🙌

Summary

Updated custom RuboCop cops to use the new RuboCop 1.x API.

Changes

Cop Base Class Migration

• belongs_to.rb and uniqueness_of.rb: Changed parent class from RuboCop::Cop::Cop to RuboCop::Cop::Base — the new base class introduced in RuboCop 1.x

Added RESTRICT_ON_SEND Constant

Both cops now define RESTRICT_ON_SEND to explicitly declare which methods they should trigger on:

• BelongsTo: [:belongs_to]
• UniquenessOf: [:validates, :validates_uniqueness_of]

This replaces the old pattern of using def_node_matcher to filter methods in on_send, and provides better performance by having RuboCop pre-filter calls.

Removed Redundant Matcher

• BelongsTo: Removed def_node_matcher :belongs_to? since RESTRICT_ON_SEND handles the filtering

Updated Offense Reporting API

Changed from add_offense(node, location: :selector) to add_offense(node.loc.selector) — the new preferred API for specifying offense location.

Updated Test Expectations

Test files now expect the new offense message format that includes the cop name prefix (e.g., DatabaseValidations/BelongsTo: Use 'db_belongs_to'. instead of just Use 'db_belongs_to'.).