Security request: Create limitations for API calls

[Fmstrat]

Issue

Impacted version: Latest

Deployment mode: Standalone behind nginx in docker

Problem description:
When using the API, there is no way to create limitations on access for a token. For instance, I would like to create a feature in my Mobile App to allow for submission of issues directly from the application.

However, the API key could be obtained from the source, and as it stands, this means that even if I set up a separate user as a "guest" they could still acquire any code from pull requests, and see all issues.

This request is to create different levels of tokens, one of which is to just create issues.