feat: implement platform handler creation

also refactor public and internal api to support transaction between
multiple methods

#2

pkg/platform.go

@@ -0,0 +1,25 @@
+package synchronizator
+
+type PlatformClass interface {
+	// How to transform the struct into a node. It needs to return the class,
+	// name and a []byte representation of the metadata.
+	//
+	// - name: A user friendly name
+	// - metadata: Arbitrary data. This will be stored as a jsonb in the database
+	//
+	ToNode() (string, []byte, error)
+
+	// How to transform a node into the struct. This method should modify the
+	// struct directly as it receives a pointer.
+	//
+	// - name: A user friendly name
+	// - metadata: Arbitrary data. This is stored as a jsonb in the database
+	FromNode(string, []byte) error
+}
+
+// Utility struct to represent a collection of nodes, it's a [Node] itself so all
+// the node's functionality is available.
+type Platform struct {
+	Node                      // Underlaying node info
+	collections []*Collection // Child nodes
+}