Remove the missing_ok parameter from metadata.validate()

[candleindark]

Closes #421.

Removes the missing_ok parameter from dandischema.metadata.validate(). As detailed in #421, missing_ok is a brittle feature that does not reliably suppress "missing field" errors (it misses required fields enforced by custom validators, and otherwise relies on substring-matching a jsonschema message) and is unused outside this repo's own tests.

Changes

• Remove the missing_ok parameter from validate() and its error-filtering branch.
• Delete the _validate_obj_json() helper, which became a pure pass-through to validate_json() once missing_ok was gone; its four callers now call validate_json() directly.
• Remove the associated tests (test_missing_ok, test_missing_ok_error, and the TestValidateObjJson class, whose subject is gone; validate_json is already covered in test_utils.py).

This is a breaking change to the public validate() signature. The usage survey in #421 found no caller passing missing_ok outside this repo's tests, so this is a hard removal rather than a deprecation.

Diffstat

 dandischema/metadata.py            |  52 ++--------
 dandischema/tests/test_metadata.py | 201 +------------------------------------
 2 files changed, 7 insertions(+), 246 deletions(-)

Test plan

• tox -e typing,lint
• python -m pytest dandischema (258 passed, 19 skipped; skips are network/instance-name gated)

[codecov]

Codecov Report

❌ Patch coverage is 14.28571% with 6 lines in your changes missing coverage. Please review.
✅ Project coverage is 47.53%. Comparing base (d752738) to head (e9f93a9).

Files with missing lines	Patch %	Lines
dandischema/metadata.py	0.00%	6 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #422      +/-   ##
==========================================
- Coverage   48.31%   47.53%   -0.79%     
==========================================
  Files          19       19              
  Lines        2434     2371      -63     
==========================================
- Hits         1176     1127      -49     
+ Misses       1258     1244      -14     

Flag	Coverage Δ
unittests	47.53% <14.28%> (-0.79%)	⬇️

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