tsk-58: Update names of Contact endpoint (#67)

Closes #58

Reviewed-on: phoenix/textsender-api#67
Co-authored-by: phoenix <kundeng00@pm.me>
Co-committed-by: phoenix <kundeng00@pm.me>

internal/store/mock/contact_store.go

@@ -3,6 +3,7 @@ package mock
 import (
 	"context"
 	"errors"
+	"fmt"
 	"sync"
 
 	"git.kundeng.us/phoenix/textsender-models/tx0/contact"
@@ -116,3 +117,30 @@ func (m *MockContactStore) ContactExists(ctx context.Context, phoneNumber string
 
 	return exists, nil
 }
+
+func (m *MockContactStore) UpdateNames(ctx context.Context, con *contact.Contact, firstname *string, lastname *string, nickname *string) (int64, error) {
+	m.mu.Lock()
+	defer m.mu.Unlock()
+
+	if m.Error != nil {
+		return 0, m.Error
+	} else if firstname == nil && lastname == nil && nickname == nil {
+		return 0, fmt.Errorf("Names are not provided")
+	} else {
+		if c, exists := m.Contacts[*con.Id]; !exists {
+			return 0, fmt.Errorf("Contact does not exist")
+		} else {
+			if firstname != nil {
+				c.Firstname = firstname
+			}
+			if lastname != nil {
+				c.Lastname = lastname
+			}
+			if nickname != nil {
+				c.Nickname = nickname
+			}
+		}
+	}
+
+	return 0, nil
+}