<!--IssueSummary start--> <details> <summary> Everyone can contribute. [Help move this issue forward](https://handbook.gitlab.com/handbook/marketing/developer-relations/contributor-success/community-contributors-workflows/#contributor-links) while earning points, leveling up and collecting rewards. </summary> - [Close this issue](https://contributors.gitlab.com/manage-issue?action=close&projectId=278964&issueIid=587133) </details> <!--IssueSummary end--> Implement create service for v2 approval rules. The service should: - Check authorization and validation - Create `MergeRequests::ApprovalRule` with: - `origin: :merge_request` - `project_id` from merge request's target project - Default `approvals_required: 0` if not specified - Default `rule_type: :regular` if not specified - Associate rule with merge request via `MergeRequests::ApprovalRulesMergeRequest` join table - Assign user approvers (if user_ids provided) - Assign group approvers (if group_ids provided) - Return ServiceResponse with success/error Reference: [POC implementation](https://gitlab.com/gitlab-org/gitlab/-/blob/e8e6a5dfaf484ebd3ccd8b06029a1ddfbbb5ecf5/ee/app/services/merge_requests/v2_approval_rules/create_service.rb) in `poc/v2-approval-rules-complete` branch.