Add constraint to `profile_authority_add` to make sure it's a verified identity

[beeman]

Currently, the profile_authority_add does not verify if an authority actually exists and is owned by the profile owner. They can literally add any valid Solana Public Key.

To fix this, the profile_authority_add should have a constraint or check that makes sure that the new_authority argument that is passed in exists in the profile.signers array and is verified by the community that's passed in as the community account on the profile_authority_add.

This will ensure that the user has access to the wallets they want to add as an authority.