Add missing comments

Firebase/Auth/Source/AuthProviders/Phone/FIRPhoneAuthProvider.m

@@ -429,6 +429,13 @@ - (void)verifyClientWithCompletion:(FIRVerifyClientCallback)completion {
   }];
 }
 
+/** @fn reCAPTCHAURLWithEventID:completion:
+    @brief Constructs a URL used for opening a reCAPTCHA app verification flow using a given event
+        ID.
+    @param eventID The event ID used for this purpose.
+    @param completion The callback invoked after the URL has been constructed or an error
+        has been encountered.
+ */
 - (void)reCAPTCHAURLWithEventID:(NSString *)eventID completion:(FIRReCAPTCHAURLCallBack)completion {
   [self fetchAuthDomainWithCompletion:^(NSString *_Nullable authDomain,
                                         NSError *_Nullable error) {
@@ -457,6 +464,12 @@ - (void)reCAPTCHAURLWithEventID:(NSString *)eventID completion:(FIRReCAPTCHAURLC
   }];
 }
 
+
+/** @fn fetchAuthDomainWithCompletion:completion:
+    @brief Fetches the auth domain associated with the Firebase Project.
+    @param completion The callback invoked after the auth domain has been constructed or an error
+        has been encountered.
+ */
 - (void)fetchAuthDomainWithCompletion:(FIRFetchAuthDomainCallback)completion {
   FIRGetProjectConfigRequest *request =
       [[FIRGetProjectConfigRequest alloc] initWithRequestConfiguration:_auth.requestConfiguration];

Firebase/Auth/Source/FIRAuthDefaultUIDelegate.h

@@ -20,6 +20,11 @@
 
 NS_ASSUME_NONNULL_BEGIN
 
+/** @class FIRAuthDefaultUIDelegate
+    @brief Class responsible for providing a default FIRAuthUIDelegte.
+    @remarks This class should be used in the case that a UIDelegate was expected and necessary to
+        continue a given flow, but none was provided.
+ */
 @interface FIRAuthDefaultUIDelegate : NSObject <FIRAuthUIDelegate>
 
 /** @fn defaultUIDelegate

Firebase/Auth/Source/FIRAuthURLPresenter.h

@@ -35,6 +35,9 @@ typedef void (^FIRAuthURLPresentationCompletion)(NSURL *_Nullable callbackURL,
  */
 typedef BOOL (^FIRAuthURLCallbackMatcher)(NSURL * _Nullable callbackURL);
 
+/** @class FIRAuthURLPresenter
+    @brief A Class responsible for presenting URL via SFSafariViewController or UIWebView.
+ */
 @interface FIRAuthURLPresenter : NSObject
 
 /** @fn presentURL:UIDelegate:callbackMatcher:completion:

Firebase/Auth/Source/FIRAuthURLPresenter.m

@@ -26,7 +26,8 @@
 
 NS_ASSUME_NONNULL_BEGIN
 
-@interface FIRAuthURLPresenter () <SFSafariViewControllerDelegate, FIRAuthWebViewDelegate>
+@interface FIRAuthURLPresenter () <SFSafariViewControllerDelegate,
+                                   FIRAuthWebViewControllerDelegate>
 @end
 
 @implementation FIRAuthURLPresenter {

Firebase/Auth/Source/FIRAuthWebView.h

@@ -18,6 +18,9 @@
 
 NS_ASSUME_NONNULL_BEGIN
 
+/** @class FIRAuthWebView
+    @brief A class reponsible for creating a UIWebview for use within Firebase Auth.
+ */
 @interface FIRAuthWebView : UIView
 
 /** @property webView

Firebase/Auth/Source/FIRAuthWebViewController.h

@@ -20,7 +20,10 @@
 
 NS_ASSUME_NONNULL_BEGIN
 
-@protocol FIRAuthWebViewDelegate <NSObject>
+/** @protocol FIRAuthWebViewControllerDelegate
+    @brief Defines a delegate for FIRAuthWebViewController
+ */
+@protocol FIRAuthWebViewControllerDelegate <NSObject>
 
 /** @fn webViewController:canHandleURL:
     @brief Determines if a URL should be handled by the delegate.
@@ -45,6 +48,9 @@ NS_ASSUME_NONNULL_BEGIN
 
 @end
 
+/** @class FIRAuthWebViewController
+    @brief Reponsible for creating a UIViewController for presenting a FIRAutWebView.
+ */
 @interface FIRAuthWebViewController : UIViewController
 
 /** @fn initWithNibName:bundle:
@@ -59,7 +65,7 @@ NS_ASSUME_NONNULL_BEGIN
 - (instancetype)initWithCoder:(NSCoder *)aDecoder NS_UNAVAILABLE;
 
 - (instancetype)initWithURL:(NSURL *)URL
-                   delegate:(__weak id<FIRAuthWebViewDelegate>)delegate
+                   delegate:(__weak id<FIRAuthWebViewControllerDelegate>)delegate
     NS_DESIGNATED_INITIALIZER;
 
 @end

Firebase/Auth/Source/FIRAuthWebViewController.m

@@ -32,7 +32,7 @@ @implementation FIRAuthWebViewController {
   /** @var _delegate
       @brief The delegate to call.
    */
-  __weak id<FIRAuthWebViewDelegate> _delegate;
+  __weak id<FIRAuthWebViewControllerDelegate> _delegate;
 
   /** @var _webView;
       @brief The web view instance for easier access.
@@ -41,7 +41,7 @@ @implementation FIRAuthWebViewController {
 }
 
 - (instancetype)initWithURL:(NSURL *)URL
-                   delegate:(__weak id<FIRAuthWebViewDelegate>)delegate {
+                   delegate:(__weak id<FIRAuthWebViewControllerDelegate>)delegate {
   self = [super initWithNibName:nil bundle:nil];
   if (self) {
     _URL = URL;

Firebase/Auth/Source/Public/FIRAuthUIDelegate.h

@@ -23,8 +23,7 @@ NS_ASSUME_NONNULL_BEGIN
 
 /** @protocol FIRAuthUIDelegate
     @brief A protocol to handle user interface interactions for Firebase Auth.
-*/
-
+ */
 @protocol FIRAuthUIDelegate  <NSObject>
 
 /** @fn presentViewController:animated:completion: