Documents some critical stats we're tracking.

WordPressAuthenticator/NUX/NUXLinkAuthViewController.swift

@@ -33,6 +33,8 @@ class NUXLinkAuthViewController: LoginViewController {
         if let linkSource = loginFields.meta.emailMagicLinkSource {
             switch linkSource {
             case .signup:
+                // This stat is part of a funnel that provides critical information.  Before
+                // making ANY modification to this stat please refer to: p4qSXL-35X-p2
                 WordPressAuthenticator.track(.createdAccount, properties: ["source": "email"])
                 WordPressAuthenticator.track(.signupMagicLinkSucceeded)
             case .login:

WordPressAuthenticator/Signin/LoginPrologueViewController.swift

@@ -85,6 +85,8 @@ class LoginPrologueViewController: LoginViewController {
     }
 
     private func signupTapped() {
+        // This stat is part of a funnel that provides critical information.  Before
+        // making ANY modification to this stat please refer to: p4qSXL-35X-p2
         WordPressAuthenticator.track(.signupButtonTapped)
         performSegue(withIdentifier: NUXViewController.SegueIdentifier.showSignupMethod.rawValue, sender: self)
     }

WordPressAuthenticator/Signup/SignupGoogleViewController.swift

@@ -130,6 +130,8 @@ private extension SignupGoogleViewController {
     /// Social Signup Successful: Analytics + Pushing the Signup Epilogue.
     ///
     func socialSignupWasSuccessful(with credentials: AuthenticatorCredentials) {
+        // This stat is part of a funnel that provides critical information.  Before
+        // making ANY modification to this stat please refer to: p4qSXL-35X-p2
         WordPressAuthenticator.track(.createdAccount, properties: ["source": "google"])
         WordPressAuthenticator.track(.signupSocialSuccess)