feat: Centralized Request Processing middleware

[dave-gray101]

This PR reworks how our endpoints parse and process user input, in order to centralize and commonize that code as much as possible. This will drastically cut down the endpoint-specific code to a minimum.

Note to @mudler - this PR looks worse than it is - here's some reviewing notes to help

• core/http/middleware/request.go should be where you start - its the heart of the change and replaces core/http/ctx/fiber.go
• configuration of defaults is now a responsibility of the route function - seems a bit weird at first, but allows endpoints to be easily reused with different defaults on different paths.
• while all the endpoint files were updated, the changes all follow the same pattern:
  • A new standard header to the function was added which pulls the relevant input and config from the earlier middleware stage
  • A bunch of code is deleted as its now performed earlier by those middlewares
  • The functional code specific to the endpoint is unchanged except for variable references

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[dave-gray101]

@mudler merged in VAD, but I don't know how to test it manually yet since it's new. Please double check that :)