Add ability to save context to streams

BunqSdk.Tests/Context/ApiContextTest.cs

@@ -1,4 +1,5 @@
-using Bunq.Sdk.Context;
+using System.IO;
+using Bunq.Sdk.Context;
 using Xunit;
 
 namespace Bunq.Sdk.Tests.Context
@@ -45,5 +46,22 @@ public void TestApiContextSaveRestore()
 
             Assert.Equal(apiContextJson, apiContextRestored.ToJson());
         }
+
+        /// <summary>
+        /// Tests saving and restoring of the API context.
+        /// </summary>
+        [Fact]
+        public void TestApiContextSaveRestoreReader()
+        {
+            var buffer = new MemoryStream();
+            var apiContextJson = apiContext.ToJson();
+
+            apiContext.Save(buffer);
+
+            buffer.Seek(0, SeekOrigin.Begin);
+            var apiContextRestored = ApiContext.Restore(buffer);
+
+            Assert.Equal(apiContextJson, apiContextRestored.ToJson());
+        }
     }
 }

BunqSdk/Context/ApiContext.cs

@@ -188,7 +188,7 @@ public bool IsSessionActive()
             {
                 return false;
             }
-            
+
             var timeToExpiry = SessionContext.ExpiryTime.Subtract(DateTime.Now);
             var timeToExpiryMinimum = new TimeSpan(
                 TIME_UNIT_COUNT_NONE,
@@ -222,6 +222,22 @@ public void Save(string fileName)
             }
         }
 
+        /// <summary>
+        /// Save a JSON representation of the API Context to a given writer.
+        /// </summary>
+        public void Save(Stream stream)
+        {
+            try
+            {
+                var writer = new StreamWriter(stream, ENCODING_BUNQ_CONF);
+                writer.Write(ToJson());
+            }
+            catch (IOException exception)
+            {
+                throw new BunqException(ERROR_COULD_NOT_SAVE_API_CONTEXT, exception);
+            }
+        }
+
         /// <summary>
         /// Serialize the API Context to JSON.
         /// </summary>
@@ -253,6 +269,22 @@ public static ApiContext Restore(string fileName)
             }
         }
 
+        /// <summary>
+        /// Restores a context from a given reader.
+        /// </summary>
+        public static ApiContext Restore(Stream stream)
+        {
+            try
+            {
+                var reader = new StreamReader(stream);
+                return FromJson(reader.ReadToEnd());
+            }
+            catch (IOException exception)
+            {
+                throw new BunqException(ERROR_COULD_NOT_RESTORE_API_CONTEXT, exception);
+            }
+        }
+
         /// <summary>
         /// De-serializes a context from JSON.
         /// </summary>