Make all API models convert to camelCase

[callumforrester]

Previously, with apischema, the API models were serialized with camel case aliasing. For example, converting a Python field called foo_bar to a JSON field called fooBar and vice versa. This is to comply with the Google JSON style guide.

https://google.github.io/styleguide/jsoncstyleguide.xml?showone=Property_Name_Format#Property_Name_Format

This PR adds a custom base model with custom config primarily to preserve this change and also to prevent the ingestion of arbitrary JSON alongside a model's known fields, which apischema also did not allow.

[codecov]

Codecov Report

Merging #132 (4c35abb) into main (a7c897f) will increase coverage by 0.34%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##             main     #132      +/-   ##
==========================================
+ Coverage   74.17%   74.52%   +0.34%     
==========================================
  Files          36       37       +1     
  Lines        1034     1048      +14     
==========================================
+ Hits          767      781      +14     
  Misses        267      267              

Impacted Files	Coverage Δ
src/blueapi/core/context.py	77.04% <ø> (-1.08%)	⬇️
src/blueapi/config.py	100.00% <100.00%> (ø)
src/blueapi/core/bluesky_types.py	87.87% <100.00%> (+0.37%)	⬆️
src/blueapi/service/model.py	81.25% <100.00%> (+0.60%)	⬆️
src/blueapi/utils/__init__.py	100.00% <100.00%> (ø)
src/blueapi/utils/base_model.py	100.00% <100.00%> (ø)
src/blueapi/worker/event.py	90.00% <100.00%> (+0.20%)	⬆️
src/blueapi/worker/task.py	73.33% <100.00%> (+0.91%)	⬆️

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