FEATURE: Rename 'Discourse SSO' to DiscourseConnect (#11978)

The 'Discourse SSO' protocol is being rebranded to DiscourseConnect. This should help to reduce confusion when 'SSO' is used in the generic sense.

This commit aims to:
- Rename `sso_` site settings. DiscourseConnect specific ones are prefixed `discourse_connect_`. Generic settings are prefixed `auth_`
- Add (server-side-only) backwards compatibility for the old setting names, with deprecation notices
- Copy `site_settings` database records to the new names
- Rename relevant translation keys
- Update relevant translations

This commit does **not** aim to:
- Rename any Ruby classes or methods. This might be done in a future commit
- Change any URLs. This would break existing integrations
- Make any changes to the protocol. This would break existing integrations
- Change any functionality. Further normalization across DiscourseConnect and other auth methods will be done separately

The risks are:
- There is no backwards compatibility for site settings on the client-side. Accessing auth-related site settings in Javascript is fairly rare, and an error on the client side would not be security-critical.
- If a plugin is monkey-patching parts of the auth process, changes to locale keys could cause broken error messages. This should also be unlikely. The old site setting names remain functional, so security-related overrides will remain working.

A follow-up commit will be made with a post-deploy migration to delete the old `site_settings` rows.

spec/components/validators/enable_invite_only_validator_spec.rb

@@ -7,8 +7,8 @@ RSpec.describe EnableInviteOnlyValidator do
 
   context "when sso is enabled" do
     before do
-      SiteSetting.sso_url = "https://example.com/sso"
-      SiteSetting.enable_sso = true
+      SiteSetting.discourse_connect_url = "https://example.com/sso"
+      SiteSetting.enable_discourse_connect = true
     end
 
     it "is valid when false" do
@@ -18,7 +18,7 @@ RSpec.describe EnableInviteOnlyValidator do
     it "is isn't value for true" do
       expect(subject.valid_value?('t')).to eq(false)
       expect(subject.error_message).to eq(I18n.t(
-        'site_settings.errors.sso_invite_only'
+        'site_settings.errors.discourse_connect_invite_only'
       ))
     end
   end

spec/components/validators/enable_sso_validator_spec.rb

@@ -8,7 +8,7 @@ RSpec.describe EnableSsoValidator do
   describe '#valid_value?' do
     describe "when 'sso url' is empty" do
       before do
-        SiteSetting.sso_url = ""
+        SiteSetting.discourse_connect_url = ""
       end
 
       describe 'when val is false' do
@@ -22,7 +22,7 @@ RSpec.describe EnableSsoValidator do
           expect(subject.valid_value?('t')).to eq(false)
 
           expect(subject.error_message).to eq(I18n.t(
-            'site_settings.errors.sso_url_is_empty'
+            'site_settings.errors.discourse_connect_url_is_empty'
           ))
         end
       end
@@ -31,7 +31,7 @@ RSpec.describe EnableSsoValidator do
     describe "when invite_only is set" do
       before do
         SiteSetting.invite_only = true
-        SiteSetting.sso_url = 'https://example.com/sso'
+        SiteSetting.discourse_connect_url = 'https://example.com/sso'
       end
 
       it 'allows a false value' do
@@ -41,14 +41,14 @@ RSpec.describe EnableSsoValidator do
       it "doesn't allow true" do
         expect(subject.valid_value?('t')).to eq(false)
         expect(subject.error_message).to eq(I18n.t(
-          'site_settings.errors.sso_invite_only'
+          'site_settings.errors.discourse_connect_invite_only'
         ))
       end
     end
 
     describe "when 'sso url' is present" do
       before do
-        SiteSetting.sso_url = "https://www.example.com/sso"
+        SiteSetting.discourse_connect_url = "https://www.example.com/sso"
       end
 
       describe 'when value is false' do

spec/components/validators/sso_overrides_email_validator_spec.rb

@@ -8,8 +8,8 @@ RSpec.describe SsoOverridesEmailValidator do
   describe '#valid_value?' do
     describe "when 'email editable' is true" do
       before do
-        SiteSetting.sso_url = "https://www.example.com/sso"
-        SiteSetting.enable_sso = true
+        SiteSetting.discourse_connect_url = "https://www.example.com/sso"
+        SiteSetting.enable_discourse_connect = true
         SiteSetting.email_editable = true
       end
 
@@ -32,8 +32,8 @@ RSpec.describe SsoOverridesEmailValidator do
 
     describe "when 'email editable' is false" do
       before do
-        SiteSetting.sso_url = "https://www.example.com/sso"
-        SiteSetting.enable_sso = true
+        SiteSetting.discourse_connect_url = "https://www.example.com/sso"
+        SiteSetting.enable_discourse_connect = true
         SiteSetting.email_editable = false
       end