[fix] prevent usage of unsafe encoded characters in path segments

[dmkret]

Closes #7567
Closes #7554
Closes #7570

This PR prevents using path segments (folder names) to contain uri-decodable characters like []% and so on.

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[benmccann]

I'm not exactly sure about this. It's unclear to me what exactly it's disallowing and at the very least would need some comment explaining what is considered to be an invalid character. It's also difficult for users to understand which characters are invalid from the error message. I think we could write this whole thing in a clearer way