Prepare for 2.1.0 release. (#957)

Author: w-goog

AppAuth.podspec

@@ -1,7 +1,7 @@
 Pod::Spec.new do |s|
 
   s.name         = "AppAuth"
-  s.version      = "2.0.0"
+  s.version      = "2.1.0"
   s.summary      = "AppAuth for iOS and macOS is a client SDK for communicating with OAuth 2.0 and OpenID Connect providers."
 
   s.description  = <<-DESC

CHANGELOG.md

@@ -1,7 +1,7 @@
-# Unreleased
+# 2.1.0
 - Add SwiftUI + Swift Package Manager sample app under `Examples/Example-iOS_Swift-SPM`. ([#952](https://github.com/openid/AppAuth-iOS/pull/952))
-- Removed external browser (Safari) fallback from `OIDExternalUserAgentIOS`. If `ASWebAuthenticationSession` fails to start (e.g., Guided Access is enabled), the authorization flow now fails with an error instead of opening an external browser.
-- Added `resumeExternalUserAgentFlowWithURL:error:` to `OIDExternalUserAgentSession` protocol. This method returns errors via an out-parameter instead of throwing `NSException` in invalid-state scenarios. The previous `resumeExternalUserAgentFlowWithURL:` method is deprecated and forwards to the new method. Note that, as a side effect of this forwarding, the deprecated method no longer raises `NSException` (with name `OIDOAuthExceptionInvalidAuthorizationFlow`) on invalid state — it now returns `NO` silently. Migrate to the `resumeExternalUserAgentFlowWithURL:error:` variant to inspect the cause. ([#955](https://github.com/openid/AppAuth-iOS/pull/955))
+- Removed external browser (Safari) fallback from `OIDExternalUserAgentIOS`. If `ASWebAuthenticationSession` fails to start (e.g., Guided Access is enabled), the authorization flow now fails with an error instead of opening an external browser. ([#954](https://github.com/openid/AppAuth-iOS/pull/954))
+- Added `resumeExternalUserAgentFlowWithURL:error:` to `OIDExternalUserAgentSession` protocol, returning errors via an out-parameter instead of throwing `NSException`. The previous method is deprecated and forwards to the new one. ([#955](https://github.com/openid/AppAuth-iOS/pull/955))
 - Added `OIDErrorCodeURLMismatch` and `OIDErrorCodeInvalidAuthorizationFlow` error codes. ([#955](https://github.com/openid/AppAuth-iOS/pull/955))
 
 # 2.0.0