Required field KEY_TYPE is always None in MA lookup_keys call

[MarshallBrinn]

The key_type field is blank for all keys in the ma_ssh_key table and accordingly all calls to lookup_keys returns None. The Federation API indicates this is a required field.

We have opened a thread with the federation_api mailing list to discuss this. The proposal is that there be an advertised set of supported key types (SSH, PGP, GPG, KERBEROS, e.g.). Our CH will only support SSH and give an error if any other key_type is provided (in create or lookup). And all lookup_key queries will return key_type=SSH.

Putting this on hold until we get a little more feedback from the community.