fixed issue on multi select field while selecting single item

[parthjoshi90]

Before this

• It was required to pre-validate the values before the form was validated
  After this
• Based on the annotation based on the types provided on the field it will parse the value.

fixes #122.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (cec25c6) 94.05% compared to head (4062c67) 93.91%.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #159      +/-   ##
==========================================
- Coverage   94.05%   93.91%   -0.14%     
==========================================
  Files          11       11              
  Lines         723      723              
==========================================
- Hits          680      679       -1     
- Misses         43       44       +1     

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[samuelcolvin]

Thanks so much for looking at this, we need to change approach and also need to add tests.

[samuelcolvin]

this isn't going to work for lots of other types e.g. tuple, set, frozenset.

Instead of introspecting the python type, I'd rather we iterated over the JSON Schema and worked out which fields should take multiple values that way.

With that we can also:

• move the logic out of unflatten thus separating concerns
• cache the result per model
• have a more general solution as JSON Schema already simplifies many types into an array schema

Since we already have logic to flatten JSON Schema, we might be able to use that and therefore pass a simple dict[key, bool] to this method.