All GET and POST requests in the dashboard plugin should use access token

Right now, the communication between the browser and the "plugin" server runs over HTTP, which is OK because it is local. However, all the "network" communication should happen by using a token. This token should be generated everytime the server is started and should be destroyed after the server is closed. The "/get-token" should also return this token to the JavaScript. 

Alternate (and possibly preferred method):

We can use the gitlab_private_token which is returned to JS using `/get-token` method.  This token is sent as "PRIVATE-TOKEN: token" as header in all requests. We should check all incoming requests in the fastapi server that they contain this PRIVATE-TOKEN as the header.