Org + Contributor backend pt. 1

[DiegolMarques]

Branch name: org-contributor-relations

Task at Hand

1. Update controllers with relation handling:
   • Add to controllers/organizations.ts:
     • getOrganizationContributors
     • addContributorToOrganization
   • Add to controllers/contributors.ts:
     • getContributorOrganizations
2. Add corresponding routes:
   • GET /organizations/:id/contributors
   • POST /organizations/:id/contributors
   • GET /contributors/:id/organizations

Testing

Create test suite on the test folder. Use backend test for reference.