Validation API should be public, and accept either a schema name or an organization.sender name.

[jimduff-usds]

The public facing validator page will support validation against a few known/popular schema names, that will initially be hardcoded.

Because it is public, the UI does not know an organization name nor sender name to use. So it must submit data for validation using the schema name.

Acceptance Criteria

• This ticket is to change the validation API to accept a header with the schema name OR a header with an organization.sender name.
• Unit tests written
• Make the API public
• Confirm you didn't break the old organization.sender functionality.
• Confirm with Stephen N.
• Confirm its ok with the Xperiencites
• Update (or create?) the appropriate documentation in docs/api/

Discussion

• Should we allow schema-name based submissions for the "real" submission endpoints too?
• Current header for sender name is of the form client: organization.sender
• New form can be schema: path/schema-name
• Note that each schema knows its "topic"