Create resources

[yellalena]

• Add POST /resources endpoint.
• Process tags similar to mentors -> tags should be stored in the tags table with relation to the resources record.
• Verify:
  • The role of requestor matches with the feature flag value from Add feature flag to change level of resource creation #174
  • Members can post for public and members
  • Mentors can post for public, members and mentors
  • Admins can post for everybody
• Add a code check (or proper db constraint failure handling) and return proper error messages (utilize errors.js) for cases:
  • For post resource type description field is required
  • For video resource type link field is required
  • Every resource should have either a Description or an Attachment (filename, link), both cannot be empty.
• No attachment processing in this ticket, will be done in
• Update swagger
• Add unit tests