Allow ThingServer to accept ThingServerConfig instances directly

[rwb27]

Currently, ThingServer is initialised by supplying a dictionary of Thing subclasses and other parameters. This means the constructor of ThingServer duplicates all the arguments to the constructor of ThingServerConfig, which causes a few wrinkles.

I propose we allow ThingServer to accept a config model directly. This avoids some argument duplication and avoids revalidation of the config model.

It is, however, the case that it's more convenient in test or example code to use ThingServer in the current way, i.e. to supply the dictionary of Thing subclasses as the first argument, and other config parameters as subsequent arguments. It is also desirable to be backwards-compatible, which requires keeping this signature as an option.

I propose we allow ThingServer to accept a config model, providing backwards compatibility with the existing way of doing things. This can be done unambiguously if we make things a reserved name, i.e. it's not allowed to have a Thing on your server with the name things. In the future, we might split this out of the initialiser, such that you can either initialise a server with:

server = lt.ThingServer(config_model_or_dictionary)

or

server = lt.ThingServer.from_things(
    {"name": ThingSubclass}, settings_folder="./my_settings"
)

Avoiding revalidation should allow easier subclassing of the config model, which ought to come in handy when customising the server downstream.

I've also added:

• a property for debug to allow downstream code to see it.
• single-sourced settings_folder from the config model
• a serve method to run the server with uvicorn.run
• a test_client method to supply a test client.

I've removed the dry_run argument from serve_from_cli (in favour of testing it properly using mocker) and changed it to use the new serve method of the server. This also meant I could improve a couple of the tests by checking it produced a server in the correct state, and not just that they logged the right thing.

It is unfortunate that the number of touched files is so large. Mostly this is a result of a couple of search-and-replace operations to change ThingServer(things) to ThingServer.from_things(things) and get rid of ThingServer.from_config.

Closes #295
Closes #298
Closes #311

[barecheck]

Barecheck - Code coverage report

Total: 96.68%

Your code coverage diff: 0.04% ▴

Uncovered files and lines

File	Lines
src/labthings_fastapi/outputs/mjpeg_stream.py	195, 197, 200, 203, 255-257, 266-268, 295, 299-300, 334, 362, 438, 474
src/labthings_fastapi/server/__init__.py	290, 304-307
src/labthings_fastapi/server/cli.py	102, 163