Linking multiple PID providers

Multiple PID providers could be enabled on an installation.

• Zenodo
• Datacite etc.

At PID acquisition the PID provider could be saved (and subsequently presented as default for a user).

If systemic PID provided (i.e. without user credentials), this would require that users are not all entitled to use a specific PID provider.

PIDs should also have a type (determining schema and resolver).