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

api/command_loadtest.go

@@ -164,7 +164,7 @@ func (me *LoadTestProvider) SetupCommand(c *Context, channelId string, message s
 		if err := CreateBasicUser(client); err != nil {
 			return &model.CommandResponse{Text: "Failed to create testing environment", ResponseType: model.COMMAND_RESPONSE_TYPE_EPHEMERAL}
 		}
-		client.LoginByEmail(BTEST_TEAM_NAME, BTEST_USER_EMAIL, BTEST_USER_PASSWORD)
+		client.Login(BTEST_USER_EMAIL, BTEST_USER_PASSWORD)
 		environment, err := CreateTestEnvironmentWithTeams(
 			client,
 			utils.Range{numTeams, numTeams},