API documentation with Swagger

[JakobMiksch]

• Add the route /docs with a Swagger UI for API development, see screenshot below
• /docs does not need Basic Auth, the API routes still need it
• the UI also supports login with Basic Auth and the UI can therefore be used to access the API with the Browser
• references API docs #23
• builds on Instantly use env vars on "npm run watch" #29

TODO (After merge)

• the swagger.yaml is currently redundant with our JSON schema schema-geotiff-upload.json - we should find a way to either link the JSON schema to the Swagger config or use the swagger config to validate the input of the API --> could be moved to follow up issue
• after merge: add config file to 'klips-sdi'

[JakobMiksch]

@hwbllmnn @hblitza this is sitll kind of WIP, maybe you could have a look what you think (especially regarding the TODOs) , then I can make adaptations if needed

[hblitza]

comment define environment variables still needed? since below all are deleted

[hblitza]

LGTM, just minor.