tsk-18: Create service user (#22)

Closes #18

Reviewed-on: phoenix/textsender-auth#22
Co-authored-by: phoenix <kundeng00@pm.me>
Co-committed-by: phoenix <kundeng00@pm.me>

internal/store/mock/service_store.go

@@ -0,0 +1,74 @@
+package mock
+
+import (
+	"context"
+	"errors"
+	"sync"
+
+	"github.com/google/uuid"
+
+	"git.kundeng.us/phoenix/textsender-models/pkg/user"
+)
+
+type MockServiceUserStore struct {
+	ServiceUsers           map[uuid.UUID]*user.ServiceUser
+	ServiceUsersByUsername map[string]*user.ServiceUser
+	mu                     sync.RWMutex
+	Error                  error // Optional: simulate errors
+}
+
+func NewMockServiceUserStore() *MockServiceUserStore {
+	return &MockServiceUserStore{
+		ServiceUsers:           make(map[uuid.UUID]*user.ServiceUser),
+		ServiceUsersByUsername: make(map[string]*user.ServiceUser),
+	}
+}
+
+func (m *MockServiceUserStore) Create(ctx context.Context, user *user.ServiceUser) error {
+	m.mu.Lock()
+	defer m.mu.Unlock()
+
+	if m.Error != nil {
+		return m.Error
+	}
+
+	if user.Id == uuid.Nil {
+		user.Id = uuid.New()
+	}
+
+	if _, exists := m.ServiceUsersByUsername[user.Username]; exists {
+		return errors.New("service User with username already exists")
+	}
+
+	m.ServiceUsers[user.Id] = user
+	m.ServiceUsersByUsername[user.Username] = user
+	return nil
+}
+
+func (m *MockServiceUserStore) CheckWithUsername(ctx context.Context, username string) (bool, error) {
+	m.mu.Lock()
+	defer m.mu.Unlock()
+
+	if m.Error != nil {
+		return false, m.Error
+	}
+
+	if m.Error != nil {
+		return false, m.Error
+	}
+
+	var exists bool
+
+	for _, serviceUser := range m.ServiceUsers {
+		if serviceUser.Username == username {
+			exists = true
+			break
+		}
+	}
+
+	if !exists {
+		return exists, nil
+	} else {
+		return exists, nil
+	}
+}