Deprecate backwards-compatibility delegates in DocSpec.Spec.Schema

[StephanMeijer]

Problem

DocSpec.Spec.Schema (lines 400–516) contains 6 delegated functions that all forward to DocSpec.JSON:

• encode_without_defaults/1 → DocSpec.JSON.to_encodable/1
• to_camel_case/1 → DocSpec.JSON.to_camel_case/1
• to_snake_case/1 → DocSpec.JSON.to_snake_case/1
• decode_json/1 → DocSpec.JSON.decode/1
• decode_json!/1 → DocSpec.JSON.decode!/1
• decode_keys/1 → DocSpec.JSON.from_decoded/1

The comment says these are "kept for backwards compatibility."

Issues

• Duplicates DocSpec.JSON's documented public API
• Adds maintenance burden (two sets of @doc + @spec to keep in sync)
• Confuses library consumers about which module to use for JSON operations
• Schema is not where users would look for JSON encoding/decoding functions

Proposal

1. Add @deprecated "Use DocSpec.JSON.to_encodable/1 instead" (etc.) to each delegate
2. Document migration in CHANGELOG
3. Remove in the next major version

Files

• lib/docspec/spec/schema.ex (lines 400–516)