Persist FIRPhoneMultiFactorInfo (instead of FIRMultiFactorInfo) so that full phone number is always cached (#10296)

Author: chuanr

FirebaseAuth/Sources/MultiFactor/FIRMultiFactor.m

@@ -179,8 +179,7 @@ - (nullable instancetype)initWithCoder:(NSCoder *)aDecoder {
   self = [self init];
   if (self) {
     NSArray<FIRMultiFactorInfo *> *enrolledFactors =
-        [aDecoder decodeObjectOfClass:[NSArray<FIRMultiFactorInfo *> class]
-                               forKey:kEnrolledFactorsCodingKey];
+        [aDecoder decodeObjectForKey:kEnrolledFactorsCodingKey];
     _enrolledFactors = enrolledFactors;
     _user = [aDecoder decodeObjectOfClass:[FIRUser class] forKey:kUserCodingKey];
   }

FirebaseAuth/Sources/MultiFactor/FIRMultiFactorInfo+Internal.h

@@ -30,6 +30,14 @@ NS_ASSUME_NONNULL_BEGIN
 
 - (instancetype)initWithProto:(FIRAuthProtoMFAEnrollment *)proto;
 
+#pragma mark - NSSecureCoding
+// Note that we're not able to indicate FIRMultiFactorInfo conforming to NSSecureCoding in an
+// internal header file, so the following NSSecureCoding methods are explicitly declared.
+
+- (nullable instancetype)initWithCoder:(NSCoder *)aDecoder;
+
+- (void)encodeWithCoder:(NSCoder *)aCoder;
+
 @end
 
 NS_ASSUME_NONNULL_END

FirebaseAuth/Sources/MultiFactor/Phone/FIRPhoneMultiFactorInfo.m

@@ -23,6 +23,8 @@
 #import "FirebaseAuth/Sources/Backend/RPC/Proto/FIRAuthProtoMFAEnrollment.h"
 #import "FirebaseAuth/Sources/MultiFactor/FIRMultiFactorInfo+Internal.h"
 
+static NSString *kPhoneNumberCodingKey = @"phoneNumber";
+
 extern NSString *const FIRPhoneMultiFactorID;
 
 @implementation FIRPhoneMultiFactorInfo
@@ -36,6 +38,25 @@ - (instancetype)initWithProto:(FIRAuthProtoMFAEnrollment *)proto {
   return self;
 }
 
+#pragma mark - NSSecureCoding
+
++ (BOOL)supportsSecureCoding {
+  return YES;
+}
+
+- (nullable instancetype)initWithCoder:(NSCoder *)aDecoder {
+  self = [super initWithCoder:aDecoder];
+  if (self) {
+    _phoneNumber = [aDecoder decodeObjectOfClass:[NSString class] forKey:kPhoneNumberCodingKey];
+  }
+  return self;
+}
+
+- (void)encodeWithCoder:(NSCoder *)aCoder {
+  [super encodeWithCoder:aCoder];
+  [aCoder encodeObject:_phoneNumber forKey:kPhoneNumberCodingKey];
+}
+
 @end
 
 #endif