Add authentication config information to usage ping

Problem

Currently, we only track LDAP in the self-managed feedback we receive back in usage ping. For us to be able to better understand which authentication strategies we should invest in, we should get some basic information on what instances tend to use.

Proposal

Please add the following to usage ping under the usage_activity_by_stage_manage method. Please indicate in usage ping whether an instance is using:

• LDAP
• OmniAuth, and which provider
• SAML SSO for Groups
• Open registration (username/password registration)

Returning the number of users can be left out of this iteration. If an instance has the method configured, return true. If not, return false.

Note that each method should be tracked separately (e.g. using_ldap, using_omniauth, using_saml_sso) so we're aware when an instance is using multiple authentication methods.

Edit: I'm adding open registration as something to track, as well.

Issue readiness

• Product: issue description is accurate with an acceptable proposal for an MVC
• Engineering: issue is implementable with few remaining questions, is sufficiently broken down, and is able to be estimated