Prevent creation of attributes with invalid characters

[Magnus-Kuhn]

Readiness checklist

• I added/updated tests.
• I ensured that the PR title is good enough for the changelog.
• I labeled the PR.
• I self-reviewed the PR.

Description

This validates invalid characters in attributes when

• creating or succeeding a repository attribute
• creating or accepting a CreateAttributeRequestItem/ProposeAttributeRequestItem (in canCreate / canAccept)
• accepting a ReadAttributeRequestItem

Those validations occur mostly on the sender's side (except the canAccept CreateAttributeRequestItem).

Possibilities to expand this validation are

• incoming notifications after attribute succession
• attributeQueries
• ShareAttributeRequestItems
• applyResponseItem handlers

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

see 120 files with indirect coverage changes

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[jkoenig134]

Very nice, going down from 48 changed files to only 9!!