refactor: [shitty claude AI first try] restructure server and user services, add new test cases, and improve error handling

internal/api/user/domain/user_domain_test.go

@@ -0,0 +1,53 @@
+package domain
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestUser_Structure(t *testing.T) {
+	user := User{
+		Uuid:        "123e4567-e89b-12d3-a456-426614174000",
+		PhoneNumber: "+1234567890",
+	}
+
+	assert.Equal(t, "123e4567-e89b-12d3-a456-426614174000", user.Uuid)
+	assert.Equal(t, "+1234567890", user.PhoneNumber)
+}
+
+func TestErrUserNotFound_Error(t *testing.T) {
+	tests := []struct {
+		name        string
+		phoneNumber string
+		want        string
+	}{
+		{
+			name:        "returns formatted error message",
+			phoneNumber: "+1234567890",
+			want:        "User not found with phone number: +1234567890",
+		},
+		{
+			name:        "handles empty phone number",
+			phoneNumber: "",
+			want:        "User not found with phone number: ",
+		},
+		{
+			name:        "handles international phone number",
+			phoneNumber: "+44123456789",
+			want:        "User not found with phone number: +44123456789",
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			err := ErrUserNotFound{PhoneNumber: tt.phoneNumber}
+			assert.Equal(t, tt.want, err.Error())
+		})
+	}
+}
+
+func TestErrUserNotFound_IsError(t *testing.T) {
+	err := ErrUserNotFound{PhoneNumber: "+1234567890"}
+	assert.Implements(t, (*error)(nil), err)
+}