Validate field type on serializing

[cffls]

Validate each field in CBORSerializable during serialization. This will avoid bugs caused by incorrect type of field. For instance, when a field should be Address type, but being a string type instead, it would've been serialized successfully but failed to be deserialized.

This validation also helped discovering two minor type mismatch in unit tests. 🥳

[codecov-commenter]

Codecov Report

Merging #208 (b3bccb6) into main (95881a0) will increase coverage by 0.00%.
The diff coverage is 87.09%.

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@@           Coverage Diff           @@
##             main     #208   +/-   ##
=======================================
  Coverage   85.59%   85.60%           
=======================================
  Files          26       26           
  Lines        2853     2882   +29     
  Branches      677      693   +16     
=======================================
+ Hits         2442     2467   +25     
- Misses        304      305    +1     
- Partials      107      110    +3     

Impacted Files	Coverage Δ
pycardano/serialization.py	86.78% <86.66%> (-0.12%)	⬇️
pycardano/transaction.py	94.09% <100.00%> (+0.01%)	⬆️

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[nielstron]

Very neat! I like how this also applies to everything that is serialized very elegantly.

[nielstron]

I just tried this with the error I initially reported. Its a better error message for sure, but there is still some improvement possible :)

    builder.required_signers = ["string!"]

results in

TypeError: Field 'required_signers' should be of type typing.Union[typing.List[pycardano.hash.VerificationKeyHash], 
NoneType], got <class 'list'> instead.

The error here is that I have a list of "str" and not list of the required type, which upsets the type checker - it fails to point out the precise violation though.

I think the only reasonable fix for this would be a recursive type printer. Will look into that.

[nielstron]

Suggestion: Instead of printing the type of the violating object (which may hide recursive errors), just print the violating value? This also helps the developer debug, as they might have a better grip on where a value comes from than what type it has.

Changes the error message to

TypeError: Field 'required_signers' should be of type typing.Union[typing.List[pycardano.hash.VerificationKeyHash], 
NoneType], got ['string!'] instead.