trace2: add regions to OAuth

Add region tracing to key methods in OAuth2Client. This was deemed a good
starting point for regions due to the server interaction required to
obtain tokens. Additional regions can and should be added to additional
sections of the code that are deemed performance-critical in the future.

Author: ldennington

src/shared/Core/Authentication/OAuth/OAuth2Client.cs

@@ -183,6 +183,9 @@ public async Task<OAuth2AuthorizationCodeResult> GetAuthorizationCodeAsync(IEnum
 
         public async Task<OAuth2DeviceCodeResult> GetDeviceCodeAsync(IEnumerable<string> scopes, CancellationToken ct)
         {
+            var label = "get device code";
+            using IDisposable region = _trace2.CreateRegion(OAuth2Constants.Trace2Category, label);
+
             if (_endpoints.DeviceAuthorizationEndpoint is null)
             {
                 throw new Trace2InvalidOperationException(_trace2,
@@ -218,6 +221,9 @@ public async Task<OAuth2DeviceCodeResult> GetDeviceCodeAsync(IEnumerable<string>
 
         public async Task<OAuth2TokenResult> GetTokenByAuthorizationCodeAsync(OAuth2AuthorizationCodeResult authorizationCodeResult, CancellationToken ct)
         {
+            var label = "get token by auth code";
+            using IDisposable region = _trace2.CreateRegion(OAuth2Constants.Trace2Category, label);
+
             var formData = new Dictionary<string, string>
             {
                 [OAuth2Constants.TokenEndpoint.GrantTypeParameter] = OAuth2Constants.TokenEndpoint.AuthorizationCodeGrantType,
@@ -254,6 +260,9 @@ public async Task<OAuth2TokenResult> GetTokenByAuthorizationCodeAsync(OAuth2Auth
 
         public async Task<OAuth2TokenResult> GetTokenByRefreshTokenAsync(string refreshToken, CancellationToken ct)
         {
+            var label = "get token by refresh token";
+            using IDisposable region = _trace2.CreateRegion(OAuth2Constants.Trace2Category, label);
+
             var formData = new Dictionary<string, string>
             {
                 [OAuth2Constants.TokenEndpoint.GrantTypeParameter] = OAuth2Constants.TokenEndpoint.RefreshTokenGrantType,

src/shared/Core/Authentication/OAuth/OAuth2Constants.cs

@@ -7,6 +7,7 @@ public static class OAuth2Constants
         public const string ClientSecretParameter = "client_secret";
         public const string RedirectUriParameter = "redirect_uri";
         public const string ScopeParameter = "scope";
+        public const string Trace2Category = "oauth2";
 
         public static class AuthorizationEndpoint
         {