refactor: add jwks pkg for generating jwk sets

pkg/jwks/jwks.go

@@ -0,0 +1,49 @@
+package jwks
+
+import (
+	"crypto/rand"
+	"crypto/rsa"
+
+	"github.com/lestrrat-go/jwx/jwa"
+	"github.com/lestrrat-go/jwx/jwk"
+)
+
+type Pair struct {
+	Private jwk.Set
+	Public  jwk.Set
+}
+
+func NewJwksPair() (*Pair, error) {
+	privateKey, err := rsa.GenerateKey(rand.Reader, 2048)
+	if err != nil {
+		return nil, err
+	}
+
+	key, err := jwk.New(privateKey)
+	if err != nil {
+		return nil, err
+	}
+
+	err = jwk.AssignKeyID(key)
+	if err != nil {
+		return nil, err
+	}
+
+	err = key.Set(jwk.AlgorithmKey, jwa.RS256)
+	if err != nil {
+		return nil, err
+	}
+
+	privateKeys := jwk.NewSet()
+	privateKeys.Add(key)
+
+	publicKeys, err := jwk.PublicSetOf(privateKeys)
+	if err != nil {
+		return nil, err
+	}
+
+	return &Pair{
+		Private: privateKeys,
+		Public:  publicKeys,
+	}, nil
+}