[misc] Separate shared code dependencies (#4288)

* Separate shared code dependencies

* Fix import

* Test respective shared code

* Update openapi ref

* Fix test

* Fix test path

shared/relay/messages/address/address.go

@@ -0,0 +1,21 @@
+// Deprecated: This package is deprecated and will be removed in a future release.
+package address
+
+import (
+	"bytes"
+	"encoding/gob"
+	"fmt"
+)
+
+type Address struct {
+	URL string
+}
+
+func (addr *Address) Marshal() ([]byte, error) {
+	var buf bytes.Buffer
+	enc := gob.NewEncoder(&buf)
+	if err := enc.Encode(addr); err != nil {
+		return nil, fmt.Errorf("encode Address: %w", err)
+	}
+	return buf.Bytes(), nil
+}