designs: return error if uploading filenames with special chars

What does this MR do?

This MR completely fixes #219113 (closed) (partially fixed by !42514 (merged) ) and specifically addresses #219113 (comment 360806168) Now we return an error if the user tries to upload a file with special characters in the filename. FWIW, as @.luke mentioned it could be documented as a design management limitation.

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Does this MR meet the acceptance criteria?

Conformity

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