Enhance MySubaru API integration with improved error handling and new utility functions

- Refactor Response struct's parse method to return detailed error messages based on API error codes.
- Introduce UnixTime type for handling Unix timestamps in JSON marshaling and unmarshaling.
- Add email masking utility function to obfuscate email addresses for privacy.
- Implement containsValueInStruct function to check for substring presence in struct fields.
- Create comprehensive unit tests for UnixTime, email masking, and struct value checking.
- Update vehicle service request method documentation for clarity.

utils_test.go

@@ -128,3 +128,89 @@ func TestUrlToGen_NoApiGen(t *testing.T) {
 		t.Errorf("urlToGen(%q, %q) = %q, want %q", url, gen, got, url)
 	}
 }
+
+func TestEmailHidder(t *testing.T) {
+	tests := []struct {
+		email    string
+		expected string
+		wantErr  bool
+	}{
+		{"alex@example.com", "a**x@example.com", false},
+		{"a@example.com", "a@example.com", false},
+		{"ab@example.com", "ab@example.com", false},
+		{"", "", true},
+		{"notanemail", "", true},
+	}
+
+	for _, tt := range tests {
+		got, err := emailMasking(tt.email)
+		if (err != nil) != tt.wantErr {
+			t.Errorf("emailHidder(%q) error = %v, wantErr %v", tt.email, err, tt.wantErr)
+			continue
+		}
+		if got != tt.expected {
+			t.Errorf("emailHidder(%q) = %q, want %q", tt.email, got, tt.expected)
+		}
+	}
+}
+func TestContainsValueInStruct(t *testing.T) {
+	type TestStruct struct {
+		Name    string
+		Address string
+		Age     int
+		Note    string
+	}
+	tests := []struct {
+		s      any
+		search string
+		want   bool
+	}{
+		{
+			s:      TestStruct{Name: "Alice", Address: "123 Main St", Age: 30, Note: "VIP customer"},
+			search: "alice",
+			want:   true,
+		},
+		{
+			s:      TestStruct{Name: "Bob", Address: "456 Elm St", Age: 25, Note: "Regular"},
+			search: "elm",
+			want:   true,
+		},
+		{
+			s:      TestStruct{Name: "Charlie", Address: "789 Oak St", Age: 40, Note: "VIP"},
+			search: "vip",
+			want:   true,
+		},
+		{
+			s:      TestStruct{Name: "Diana", Address: "101 Pine St", Age: 22, Note: ""},
+			search: "xyz",
+			want:   false,
+		},
+		{
+			s:      TestStruct{Name: "", Address: "", Age: 0, Note: ""},
+			search: "",
+			want:   true, // empty string is contained in all strings
+		},
+		{
+			s:      struct{ Foo int }{Foo: 42},
+			search: "42",
+			want:   false,
+		},
+		{
+			s:      "not a struct",
+			search: "struct",
+			want:   false,
+		},
+		{
+			s:      struct{ S string }{S: "CaseInsensitive"},
+			search: "caseinsensitive",
+			want:   true,
+		},
+	}
+
+	for i, tt := range tests {
+		got := containsValueInStruct(tt.s, tt.search)
+		if got != tt.want {
+			t.Errorf("Test %d: containsStringInStruct(%#v, %q) = %v, want %v", i, tt.s, tt.search, got, tt.want)
+		}
+	}
+}