[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/id.go

@@ -0,0 +1,31 @@
+package messages
+
+import (
+	"crypto/sha256"
+	"encoding/base64"
+	"fmt"
+)
+
+const (
+	prefixLength = 4
+	peerIDSize   = prefixLength + sha256.Size
+)
+
+var (
+	prefix = []byte("sha-") // 4 bytes
+)
+
+type PeerID [peerIDSize]byte
+
+func (p PeerID) String() string {
+	return fmt.Sprintf("%s%s", p[:prefixLength], base64.StdEncoding.EncodeToString(p[prefixLength:]))
+}
+
+// HashID generates a sha256 hash from the peerID and returns the hash and the human-readable string
+func HashID(peerID string) PeerID {
+	idHash := sha256.Sum256([]byte(peerID))
+	var prefixedHash [peerIDSize]byte
+	copy(prefixedHash[:prefixLength], prefix)
+	copy(prefixedHash[prefixLength:], idHash[:])
+	return prefixedHash
+}