[Feature] New company contact types

[Yoronex]

Right now, C4 and the CEB have two workflows that are not supported in ParelPracht. Because this is the case, C4 and the CEb have created workarounds and the database gets "poisoned" with incorrect data. To support these new workflows, we should add two new contact types to ParelPracht:

• "Signatory Authorized (tekengerechtigd)". These contacts are soly present for the same reasons why we have Signee users. These people are allowed by the company to sign collaboration contracts. We should be able to add these users, such that their names are put on generated documents.
• "Assisting (ondersteunend)". These contacts are for example the people who give a lunch lecture or are helping at a company workshop. They are possible points of contact for a company collaboration, but are not in charge of any collaborations or decisions. The exact term for these types of contacts is not final yet and can be discussed.

Both these new contacts have in common that we do not necessary have contact information for all of them. Therefore, for these two contact types, the email attribute should also be optional.

Summary

• Add two new contact types.
• Make email property optional in the database.
• In the backend and frontend, make email property optional iff the contact is of one of the two aforementioned new types.