Support tags/annotations per group, attribute, enum, ...

There are many situations where an extensibility mechanism, such as tags, would be beneficial to support in Weaver.

Examples of tags:

• privacy_sensitivity: specifies the privacy level/sensitivity of a specific attribute.
• data_classification: specifies the classification of an attribute in a security context.
• db_mapping: specifies a specific data mapping for systems deriving a DDL from a semantic convention registry.
• proto_field_number: specifies a protobuf field number for a specific attribute.

Note: The semantics of the tags should be definable by the semantic conventions themselves. A namespace mechanism should also be used to allow the definition of tags whose semantics are defined and standardized by OTEL, while also enabling the community to define their own tags.

The issue names no files, tests, or entry points. Start by locating Weaver’s semantic-convention model and the validation or code-generation paths that consume groups, attributes, and enums; done would require a defined tag and namespace model covering the listed use cases.