PLT-2258 Unified login screen and related APIs (#2820)

* Unified login screen and related APIs

* Refactored login API call to be less convoluted

* Removed LDAP login prompt from invite process

* Fixed existing LDAP users being able to log in if LDAP was configured, but disabled

* Gofmt

* Future proofed login API

* Updated login APIs based on feedback

* Added additional auditing to login API

* Actually removed loginById

web/web_test.go

@@ -204,7 +204,7 @@ func TestIncomingWebhook(t *testing.T) {
 	c.RequestId = model.NewId()
 	c.IpAddress = "cmd_line"
 	api.UpdateRoles(c, user, model.ROLE_SYSTEM_ADMIN)
-	ApiClient.LoginByEmail(team.Name, user.Email, "pwd")
+	ApiClient.Login(user.Email, "pwd")
 	ApiClient.SetTeamId(team.Id)
 
 	channel1 := &model.Channel{DisplayName: "Test API Name", Name: "a" + model.NewId() + "a", Type: model.CHANNEL_OPEN, TeamId: team.Id}