[B-06293] zt_registration checks if registrant is authorized

[peeech]

zt_registration endpoint reads the content of registration request and checks in opsconsoledb.registrations db if user is in fact registered and authorized to access ZT network.

This PR:

• adds check in db if user is authorized to register
• splits KV auth-server-settings between one for devnet and one for alpha

NOTE:

• before this code is merged to main we need to open API access to Production db and update mongodb_api_key in auth-server-settings KV store.