Add endpoint to get beamline parameters

[olliesilvester]

The first version of the config server just has one endpoint to get any whitelisted file either as a string, dict, or raw bytes.

We should make the server handle common configurations more intelligently. One of the most widely used configuration files is beamlineParameters. We should add another endpoint to get this specific file. It should require a beamline parameter and work out the file location from this. It should also have an option to specify a specific parameter. If this isn't used, then just send over the entire beamlineParameter dict.

The old version of this repo had similar functionality - see https://github.com/DiamondLightSource/daq-config-server/blob/4b0a2e2e8d395381645a653ec31109181738d1be/src/daq_config_server/app.py

Acceptance Criteria

• Create + test new get_beamline_parameter endpoint which matches the above description

[DiamondJoseph]

I've started constructing a BaseModel for the i03 beamline parameters previously commited to the repo, I think it's going to end up specific enough that each beamline will need their own model, which (other than if the files are at a parameterisable path) means there's no difference between

get_file(path: Path, as_type: type[T]) -> T
    ...

beamline_parameters: I03BeamlineParameters = get_file(BEAMLINE_PARAMETERS_PATH, I03BeamlineParameters)

and a dedicated endpoint