Add pq dependency
Merge branch 'feature-database' into develop

* feature-database:
  Add pq dependency
Merge branch 'develop' into feature-main

* develop:
  Add pq dependency
Implement main()

The following setup is added to the main function:

 - Connect to PostgreSQL.
 - Create the router.
 - Start the HTTP server.
Merge branch 'feature-main' into develop

* feature-main:
  Implement main()
Merge branch 'develop' into feature-user

* develop:
  Implement main()
  Add pq dependency