First version of the OpenAPI specification (#2)

This PR contains the work done to include a first version of the Marvel API document specification (that requires further tweaking) and also, the defined how the client would be generated by the Open API library.

Reviewed-on: #2
Co-authored-by: Javier Cicchelli <javier@rock-n-code.com>
Co-committed-by: Javier Cicchelli <javier@rock-n-code.com>

Sources/MarvelService/openapi-generator-config.yaml

@@ -0,0 +1,17 @@
+# ===----------------------------------------------------------------------===
+#
+# This source file is part of the MarvelService open source project
+#
+# Copyright (c) 2025 Röck+Cöde VoF. and the MarvelService project authors
+# Licensed under the EUPL 1.2 or later.
+#
+# See LICENSE for license information
+# See CONTRIBUTORS for the list of MarvelService project authors
+#
+# ===----------------------------------------------------------------------===
+
+generate:
+    - types
+    - client
+namingStrategy: defensive
+accessModifier: public