Resolve "Services: listing, add new service, fetch a service in both frontend and the backend."

This MR replaces !29 (closed)

The difference is that this MR divides the feature into commits, one individual change per commit. The fixup commits are reactions to code review comments. MR !29 (closed) has two commits, all changes in these two commits are now divided into many split up commits and fixup commits. Since the changes are identical, all these commits are authored by @godfryd

On top of these commits there are some minor fixup commits to address some more small review comments authored by @matthijs

This MR must not be merged until all issues from !29 (closed) !39 (closed) and !41 (merged) (this MR) are resolved. If changes are approved, all the fixup commits should be squashed prior to merging.

Closes #24 (closed)