Revert 'Return HTTP status 400 if missing JWT' to 401

[aldas]

Relates to:

1. Requests missing the jwt do not result in 401 Unauthorized but instead in 400 Bad Request #38
2. Return HTTP status 400 if missing JWT #13 (comment)
3. Return default errors so they can be overridden by users #33 (use ErrJWTMissing, ErrJWTInvalid clones)

lump everything under 401.

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updated deps CI + go.mod

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