Add virtual to properties

src/Microsoft.Identity.Abstractions/ApplicationOptions/IdentityApplicationOptions.cs

@@ -37,7 +37,7 @@ public class IdentityApplicationOptions
         /// Gets or sets the 'client_id' (application ID) as it appears in the 
         /// application registration. This is the string representation of a GUID.
         /// </summary>
-        public string? ClientId { get; set; }
+        public virtual string? ClientId { get; set; }
 
         /// <summary>
         /// Flag used to enable/disable logging of Personally Identifiable Information (PII).
@@ -84,7 +84,7 @@ public class IdentityApplicationOptions
         ///   See also https://aka.ms/ms-id-web-certificates.
         /// ]]></format>
         /// </example>
-        public IEnumerable<CredentialDescription>? ClientCredentials { get; set; }
+        public virtual IEnumerable<CredentialDescription>? ClientCredentials { get; set; }
         #endregion Token acquisition
 
         #region web API

src/Microsoft.Identity.Abstractions/ApplicationOptions/MicrosoftIdentityApplicationOptions.cs

@@ -24,7 +24,7 @@ public class MicrosoftIdentityApplicationOptions : IdentityApplicationOptions
         /// and school accounts. If your application is single tenant, set this property to the tenant ID or domain name.
         /// If your application works only for Microsoft personal accounts, use "consumers".
         /// </summary>
-        public string? TenantId { get; set; }
+        public virtual string? TenantId { get; set; }
 
         /// <summary>
         /// Gets or sets the Authority to use when making OpenIdConnect calls. By default the authority is computed
@@ -43,7 +43,7 @@ public override string? Authority
         /// the app attempt to detect the Azure region automatically,
         /// use "TryAutoDetect".
         /// </summary>
-        public string? AzureRegion { get; set; }
+        public virtual string? AzureRegion { get; set; }
 
         /// <summary>
         /// Specifies the capabilities of the client (for instance {"cp1", "cp2"}). This is