Feature Request: Generalize :username Validator for Broader Use

[alexskr]

The new :username validator added in #166 enforces constraints suitable for usernames:

• 3–32 characters
• starts with a letter
• contains only ASCII letters, digits, dots, and underscores
• excludes invisible or reserved terms

Request:

Generalize this validator by renaming it to something like :identifier, :safe_token, or :clean_name, so it’s not limited to usernames. These rules are broadly useful for other user-supplied attributes that require safe, human-readable strings — e.g., acronyms, labels, slugs.

Rationale:

The current :username name implies a user-account-specific use, but the underlying validation logic is more generally applicable as a datatype constraint.

Acronym validation implemented at the model level for ontologies and slices, but is inconsistently applied across other acronyms in projects, groups, and categories.

Relevant issues:

• Input Validation Issue for Project Acronyms bioportal-project#341