[Cal-4] Calendar microservice

[CommanderStorm]

This is one PR in the calendar PR-Train (#221)

Proposed Changes

• This PR migrates the calendar API into its Microservice
• The core reasoning behind this is simple:
  • Whenever we redeploy the server, we lose the calendar data
  • Reacquiring this data takes a long time
  • Migrating this into its microservice makes sense, as I can then only redeploy if really needed

How to test this PR

1. Honestly, there is no critical part that needs reviewing, as this is just a code-move

How has this been tested?

• see if it compiles ;)
• test if the core APIs (search/details) still work

Checklist:

• I have updated the documentation / No need to update the documentation
• I have run the linter