Created an ENV variable for controlling USER registrations on Vulcan app (Enabled by Default)

[smarlaku820]

• Created an ENV variable (VULCAN_ENABLE_USER_REGISTRATION) in vulcan.default.yml file
• Updated the config/initializers accordingly
• Created a Boolean helper function
• Updated the view to display User "Register" form based on the outcome of the Boolean helper function

[rlakey]

Vanessa the goal was to allow us to disable local user registration while still keeping local login enabled for emergency access but not allow anyone to randomly register new local accounts.

Also to keep the current default behavior of local login and registration enabled.

[vanessuniq]

Got it, will the registration be by invitation only if registration disabled?
if yes, is registration by invitation enabled?

[rlakey]

No this is more for if we are using another authentication method such as LDAP or OIDC where local logins are not needed.

[vanessuniq]

Also add the new env VULCAN_ENABLE_USER_REGISTRATION to the doc (/docs/config.md)