Add a method to validate email

Signed-off-by: Nikolai Rodionov <iam@allanger.xyz>

internal/api/v1/public_accounts.go

@@ -105,3 +105,12 @@ func (a *PublicAccountService) SignUp(ctx context.Context, in *accounts.SignUpRe
 		},
 	}, nil
 }
+
+// Check if an email is already used by an account
+func (a *PublicAccountService) IsEmailAvailable(ctx context.Context, in *accounts.IsEmailUsedRequest) (*accounts.IsEmailUsedResponse, error) {
+	exists, err := a.accountsCtrl.IsExist(ctx, in.GetEmail())
+	if err != nil {
+		return nil, status.Error(codes.Aborted, "Couldn't check email availability")
+	}
+	return &accounts.IsEmailUsedResponse{Used: exists}, nil
+}