[PM-5645] Cosmos DB Grant Storage (#3634)

* table storage grants

* simple shard on storage accounts

* use is not

* cosmos grant repo

* remove single storage connection string

* some fixes to dapper grant repo

* pattern matching

* add fallback to base PersistedGrantStore

* service collection extension cleanup

* cleanup

* remove unused Id

* empty string rowkey

* fix sharding method logic

* ttl for cosmos

* make ttl an int

* fixes to cosmos implementation

* fix partition key values

* catch notfound exceptions

* indenting

* update grantitem with custom serialization

* use new transform helpers

* grantloader perf test tool

* ref

* remove grant loader project

* remove table storage implementation

* remove table storage stuff

* all redis fallback to build to null

* revert sln file change

* EOF new line

* remove trailing comma

* lint fixes

* add grant to names

* move cosmos serilaizer to utils

* add some .net 8 keyed service comments

* EnableContentResponseOnWrite

* Fix type in EF grant repository

src/Core/Utilities/CoreHelpers.cs

@@ -338,16 +338,50 @@ public static class CoreHelpers
         return Encoding.UTF8.GetString(Base64UrlDecode(input));
     }
 
+    /// <summary>
+    /// Encodes a Base64 URL formatted string.
+    /// </summary>
+    /// <param name="input">Byte data</param>
+    /// <returns>Base64 URL formatted string</returns>
     public static string Base64UrlEncode(byte[] input)
     {
-        var output = Convert.ToBase64String(input)
+        // Standard base64 encoder
+        var standardB64 = Convert.ToBase64String(input);
+        return TransformToBase64Url(standardB64);
+    }
+
+    /// <summary>
+    /// Transforms a Base64 standard formatted string to a Base64 URL formatted string.
+    /// </summary>
+    /// <param name="input">Base64 standard formatted string</param>
+    /// <returns>Base64 URL formatted string</returns>
+    public static string TransformToBase64Url(string input)
+    {
+        var output = input
             .Replace('+', '-')
             .Replace('/', '_')
             .Replace("=", string.Empty);
         return output;
     }
 
+    /// <summary>
+    /// Decodes a Base64 URL formatted string.
+    /// </summary>
+    /// <param name="input">Base64 URL formatted string</param>
+    /// <returns>Data as bytes</returns>
     public static byte[] Base64UrlDecode(string input)
+    {
+        var standardB64 = TransformFromBase64Url(input);
+        // Standard base64 decoder
+        return Convert.FromBase64String(standardB64);
+    }
+
+    /// <summary>
+    /// Transforms a Base64 URL formatted string to a Base64 standard formatted string.
+    /// </summary>
+    /// <param name="input">Base64 URL formatted string</param>
+    /// <returns>Base64 standard formatted string</returns>
+    public static string TransformFromBase64Url(string input)
     {
         var output = input;
         // 62nd char of encoding
@@ -370,8 +404,8 @@ public static class CoreHelpers
                 throw new InvalidOperationException("Illegal base64url string!");
         }
 
-        // Standard base64 decoder
-        return Convert.FromBase64String(output);
+        // Standard base64 string output
+        return output;
     }
 
     public static string PunyEncode(string text)