Implemented Vault integration in k-s-a

@viktor.popov, @alexander.holodov & @damyan.mitev: Can you please review these changes?

handler/generate_keypair.go

@@ -40,7 +40,7 @@ func (s *KeyStorageServerImpl) GenerateKeyPair(ctx context.Context,
 	auth := s.CreateAuthentication(ctx)
 
 	client := &client.DataStorageClientImpl{}
-	client.SetUpClient(auth, s.DataStorageUrl, s.CertFilePath, s.KeyFilePath, s.CaCertFilePath, s.MaxMessageSize)
+	client.SetUpClient(auth, s.DataStorageUrl, s.CertPEM, s.KeyPEM, s.CaCertPEM, s.MaxMessageSize)
 	defer client.CloseClient()
 
 	generateKeyPairResponse := &api.GenerateKeyPairResponse{}
@@ -94,7 +94,7 @@ func (s *KeyStorageServerImpl) GenerateKeyPair(ctx context.Context,
 	}
 
 	if generateKeyPairResponse.StatusList == nil || len(generateKeyPairResponse.StatusList) == 0 {
-		encryptedAesKeyBytes, err := rsaEncryptWithServerKey(s.VereignCertFilePath, aesKeyBytes, []byte("aeskeys"))
+		encryptedAesKeyBytes, err := rsaEncryptWithServerKey(s.VereignCertPEM, aesKeyBytes, []byte("aeskeys"))
 		if err != nil {
 			log.Printf("Error: %v", err)
 			generateKeyPairResponse.StatusList = utils.AddStatus(generateKeyPairResponse.StatusList,
@@ -109,7 +109,7 @@ func (s *KeyStorageServerImpl) GenerateKeyPair(ctx context.Context,
 	}
 
 	if generateKeyPairResponse.StatusList == nil || len(generateKeyPairResponse.StatusList) == 0 {
-		encryptedPrivateKeyNonceBytes, err := rsaEncryptWithServerKey(s.VereignCertFilePath, privateKeyNonce, []byte("nonce"))
+		encryptedPrivateKeyNonceBytes, err := rsaEncryptWithServerKey(s.VereignCertPEM, privateKeyNonce, []byte("nonce"))
 		if err != nil {
 			log.Printf("Error: %v", err)
 			generateKeyPairResponse.StatusList = utils.AddStatus(generateKeyPairResponse.StatusList,
@@ -176,8 +176,8 @@ func generateKeyPair(keySize int) ([]byte, []byte, error) {
 	return privateKeyBytes, publicKeyBytes, nil
 }
 
-func rsaEncryptWithServerKey(certFilePath string, message []byte, label []byte) ([]byte, error) {
-	serverCertificate, err := readCertificateFromFile(certFilePath)
+func rsaEncryptWithServerKey(certPEM []byte, message []byte, label []byte) ([]byte, error) {
+	serverCertificate, err := readCertificateFromPEM(certPEM)
 	if err != nil {
 		log.Printf("Error: %v", err)
 		return nil, err