Add Rest API Backend

[marcelldls]

An additional "backend" for FastCS which provides a RestAPI.
The API is fully discoverable and demoable from the autogenerated "Swagger gui" at "{domain}/docs" and the schema can be retrived from "{domain}/openapi.json", all thanks to FastAPI.

The following considersations have been taken to conform with restful design:

• Attributes can be read using a GET request to "{domain}/{attribute-name}" (note if sub-controller then {domain}/{subcontroller name}/{attribute-name}" etc.)
  • A successful request receives response of status code 200 and a payload of json: {"value": value}
• Attributes can be written using a PUT request to "{domain}/{attribute-name}" etc.
  • A PUT request is used rather than a GET of "{domain}/{attribute-name}/{value}" to not be triggered accidentally (not "safe")
  • A PUT request is used over a POST as the action is idempotent
  • The request would have a payload of json: {"value": value}
  • A 204 response to confirm the request as there is no information to return
  • FastAPI automatically deals with wrong types an will issue a 422 error with message
• Commands can be triggered using an empty PUT to "{domain}/{command-name}"
  • A 204 response to confirm the request as there is no information to return

I follow a similar pattern to the Tango "backend" to create the server and do some testing, so any feedback from #66 should feed into this

[codecov]

Codecov Report

Attention: Patch coverage is 94.80519% with 4 lines in your changes missing coverage. Please review.

Project coverage is 86.74%. Comparing base (5256be3) to head (ff7da53).
Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
src/fastcs/backends/rest/rest.py	95.58%	3 Missing ⚠️
src/fastcs/backends/rest/backend.py	88.88%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #69      +/-   ##
==========================================
+ Coverage   86.10%   86.74%   +0.63%     
==========================================
  Files          23       25       +2     
  Lines         979     1056      +77     
==========================================
+ Hits          843      916      +73     
- Misses        136      140       +4     

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[GDYendell]

Looks good. A few comments.

I assume the test utilities have just been copied from the tango PR for now and most of it can be shared between backends once merged?

[marcelldls]

Looks good. A few comments.

I assume the test utilities have just been copied from the tango PR for now and most of it can be shared between backends once merged?

Thank you for the review Gary. I found a few tricks when I did the web api testing and fed this back into Tango. Since we will add p4p I did not look at softioc...

[marcelldls]

@GDYendell Updated the testing inline with feedback from #66