Modify custom dtype example to use only public API

[chuckwondo]

Modify custom dtype example to use only public API. As part of this effort, move/deprecate any types or functions currently inaccessible from the public API, but should be.

• Internally change all imports of DataTypeValidationError to import from zarr.errors and deprecate imports of DataTypeValidationError from all other modules.

TODO:

• Add unit tests and/or doctests in docstrings
• Add docstrings and API docs for any new/modified user-facing classes and functions
• New/modified features documented in docs/user-guide/*.md
• Changes documented as a new file in changes/
• GitHub Actions have all passed
• Test coverage is 100% (Codecov passes)

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 93.55%. Comparing base (0b431e6) to head (186e01b).

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #4052      +/-   ##
==========================================
+ Coverage   93.53%   93.55%   +0.01%     
==========================================
  Files          88       88              
  Lines       11917    11949      +32     
==========================================
+ Hits        11147    11179      +32     
  Misses        770      770              

Files with missing lines	Coverage Δ
src/zarr/core/dtype/__init__.py	100.00% <100.00%> (ø)
src/zarr/core/dtype/common.py	86.20% <100.00%> (+1.02%)	⬆️
src/zarr/core/dtype/npy/bool.py	100.00% <100.00%> (ø)
src/zarr/core/dtype/npy/bytes.py	99.50% <100.00%> (+<0.01%)	⬆️
src/zarr/core/dtype/npy/complex.py	97.61% <100.00%> (+0.02%)	⬆️
src/zarr/core/dtype/npy/float.py	98.03% <100.00%> (+0.01%)	⬆️
src/zarr/core/dtype/npy/int.py	99.38% <100.00%> (+<0.01%)	⬆️
src/zarr/core/dtype/npy/string.py	97.69% <100.00%> (+0.01%)	⬆️
src/zarr/core/dtype/npy/structured.py	92.66% <100.00%> (+0.04%)	⬆️
src/zarr/core/dtype/npy/time.py	98.86% <100.00%> (+<0.01%)	⬆️
... and 4 more

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[chuckwondo]

@d-v-b, I believe I've covered everything, except for renaming check_dtype_spec_v2 to is_dtype_spec_v2. Do you want me to do that too? If so, do you want me to deprecate check_dtype_spec_v2, or is that unnecessary since prior to this PR it is technically not public?

[chuckwondo]

@d-v-b, I believe I've covered everything, except for renaming check_dtype_spec_v2 to is_dtype_spec_v2. Do you want me to do that too? If so, do you want me to deprecate check_dtype_spec_v2, or is that unnecessary since prior to this PR it is technically not public?

nudge

[d-v-b]

@d-v-b, I believe I've covered everything, except for renaming check_dtype_spec_v2 to is_dtype_spec_v2. Do you want me to do that too? If so, do you want me to deprecate check_dtype_spec_v2, or is that unnecessary since prior to this PR it is technically not public?

yes, we can safely rename, as it wasn't public, despite appearing in the example.

[d-v-b]

out of abundance of caution I can open a follow-up PR that keeps the old check_... name around, with a deprecation warning.