refactor: Move OmemoBundle into omemo/

lib/src/omemo/bundle.dart

@@ -0,0 +1,42 @@
+import 'dart:convert';
+import 'package:cryptography/cryptography.dart';
+import 'package:omemo_dart/src/key.dart';
+
+class OmemoBundle {
+
+  const OmemoBundle(
+    this.id,
+    this.spkEncoded,
+    this.spkId,
+    this.spkSignatureEncoded,
+    this.ikEncoded,
+    this.opksEncoded,
+  );
+  final String id;
+  /// The SPK but base64 encoded
+  final String spkEncoded;
+  final String spkId;
+  /// The SPK signature but base64 encoded
+  final String spkSignatureEncoded;
+  /// The IK but base64 encoded
+  final String ikEncoded;
+  /// The mapping of a OPK's id to the base64 encoded data
+  final Map<String, String> opksEncoded;
+
+  OmemoPublicKey get spk {
+    final data = base64Decode(spkEncoded);
+    return OmemoPublicKey.fromBytes(data, KeyPairType.x25519);
+  }
+
+  OmemoPublicKey get ik {
+    final data = base64Decode(ikEncoded);
+    return OmemoPublicKey.fromBytes(data, KeyPairType.ed25519);
+  }
+
+  OmemoPublicKey getOpk(String id) {
+    final data = base64Decode(opksEncoded[id]!);
+    return OmemoPublicKey.fromBytes(data, KeyPairType.x25519);
+  }
+
+  List<int> get spkSignature => base64Decode(spkSignatureEncoded);
+}