move identityserver libs into core

src/Core/IdentityServer/TokenRetrieval.cs

@@ -0,0 +1,30 @@
+using Microsoft.AspNetCore.Http;
+using System;
+using System.Linq;
+
+namespace Bit.Core.IdentityServer
+{
+    public static class TokenRetrieval
+    {
+        public static Func<HttpRequest, string> FromAuthorizationHeaderOrQueryString(string headerScheme = "Bearer",
+            string qsName = "account_token")
+        {
+            return (request) =>
+            {
+                string authorization = request.Headers["Authorization"].FirstOrDefault();
+
+                if(string.IsNullOrWhiteSpace(authorization))
+                {
+                    return request.Query[qsName].FirstOrDefault();
+                }
+
+                if(authorization.StartsWith(headerScheme + " ", StringComparison.OrdinalIgnoreCase))
+                {
+                    return authorization.Substring(headerScheme.Length + 1).Trim();
+                }
+
+                return null;
+            };
+        }
+    }
+}