ensure usernames do not keep cycling

app/models/discourse_single_sign_on.rb

@@ -114,7 +114,9 @@ class DiscourseSingleSignOn < SingleSignOn
       user.email = email
     end
 
-    if SiteSetting.sso_overrides_username && user.username != username
+    if SiteSetting.sso_overrides_username &&
+        user.username != username &&
+        user.username != UserNameSuggester.fix_username(username || name || email)
       user.username = UserNameSuggester.suggest(username || name || email)
     end
 

spec/models/discourse_single_sign_on_spec.rb

@@ -88,7 +88,9 @@ describe DiscourseSingleSignOn do
     sso.lookup_or_create_user(ip_address)
 
     admin.reload
+
     expect(admin.email).to eq("test@bob.com")
+    expect(admin.username).to eq "bob_the_admin"
   end
 
   it "can fill in data on way back" do