add a CredentialBuilder

dart/lib/src/protocol/dsn.dart

@@ -9,11 +9,9 @@ class Dsn {
   });
 
   /// The Sentry.io public key for the project.
-  @visibleForTesting
   final String publicKey;
 
   /// The Sentry.io secret key for the project.
-  @visibleForTesting
   final String secretKey;
 
   /// The ID issued by Sentry.io to your project.
@@ -65,15 +63,4 @@ class Dsn {
       uri: uri,
     );
   }
-
-  String buildAuthHeader({int timestamp, String clientId}) {
-    var header = 'Sentry sentry_version=6, sentry_client=$clientId, '
-        'sentry_timestamp=$timestamp, sentry_key=${publicKey}';
-
-    if (secretKey != null) {
-      header += ', sentry_secret=${secretKey}';
-    }
-
-    return header;
-  }
 }

dart/lib/src/transport/transport.dart

@@ -30,19 +30,25 @@ class Transport {
 
   final Sdk sdk;
 
+  CredentialBuilder _credentialBuilder;
+
   Transport({
     @required SentryOptions options,
     @required this.sdk,
     @required this.platform,
     this.origin,
   })  : _options = options,
-        dsn = Dsn.parse(options.dsn);
+        dsn = Dsn.parse(options.dsn) {
+    _credentialBuilder = CredentialBuilder(
+      dsn: Dsn.parse(options.dsn),
+      clientId: sdk.identifier,
+    );
+  }
 
   Future<SentryId> send(SentryEvent event) async {
     final now = _options.clock();
 
-    var authHeader = dsn.buildAuthHeader(
-        timestamp: now.millisecondsSinceEpoch, clientId: sdk.identifier);
+    var authHeader = _credentialBuilder.build(now.millisecondsSinceEpoch);
     final headers = buildHeaders(authHeader, sdk: sdk);
 
     final data = _getEventData(
@@ -98,3 +104,31 @@ class Transport {
         'platform': platform,
       };
 }
+
+class CredentialBuilder {
+  final String authHeader;
+
+  CredentialBuilder({@required Dsn dsn, String clientId})
+      : authHeader = buildAuthHeader(
+          publicKey: dsn.publicKey,
+          secretKey: dsn.secretKey,
+          clientId: clientId,
+        );
+
+  String build(int timestamp) => '$authHeader, sentry_timestamp=$timestamp';
+
+  static String buildAuthHeader({
+    String publicKey,
+    String secretKey,
+    String clientId,
+  }) {
+    var header = 'Sentry sentry_version=6, sentry_client=$clientId, '
+        'sentry_key=${publicKey}';
+
+    if (secretKey != null) {
+      header += ', sentry_secret=${secretKey}';
+    }
+
+    return header;
+  }
+}

dart/test/test_utils.dart

@@ -29,15 +29,16 @@ void testHeaders(
     'Content-Type': 'application/json',
     'X-Sentry-Auth': 'Sentry sentry_version=6, '
         'sentry_client=$sdkName/$sdkVersion, '
-        'sentry_timestamp=${fakeClockProvider().millisecondsSinceEpoch}, '
-        'sentry_key=public'
+        'sentry_key=public, '
   };
 
   if (withSecret) {
-    expectedHeaders['X-Sentry-Auth'] += ', '
-        'sentry_secret=secret';
+    expectedHeaders['X-Sentry-Auth'] += 'sentry_secret=secret, ';
   }
 
+  expectedHeaders['X-Sentry-Auth'] +=
+      'sentry_timestamp=${fakeClockProvider().millisecondsSinceEpoch}';
+
   if (withUserAgent) {
     expectedHeaders['User-Agent'] = '$sdkName/$sdkVersion';
   }