feat: add Apps endpoint and query parameter support

- add `Apps` endpoint to the `Client` struct and initialize it in
`NewClient`
- implement `doWithJsonResponse` helper to handle request execution and
JSON decoding in one step
- update `newRequest` to support passing and encoding query parameters
via `net/url`
- rename `Option` to `ClientOption` for better clarity in the
`NewClient` signature
- refactor `Ping` tests to use a more structured nested layout
- remove `option.go` and `option_test.go` as part of the configuration
refactor

clientOption_test.go

@@ -0,0 +1,54 @@
+package onspring_test
+
+import (
+	"net/http"
+	"testing"
+	"time"
+
+	"github.com/StevanFreeborn/onspring-api-sdk-go"
+)
+
+func TestWithHTTPClient(t *testing.T) {
+	t.Run("it should set a custom HTTP client on the Onsring client", func(t *testing.T) {
+		customHTTPClient := &http.Client{Timeout: 10 * time.Second}
+
+		clientWithCustomHTTP := onspring.NewClient(
+			"test-api-key",
+			onspring.WithHTTPClient(customHTTPClient),
+		)
+
+		if clientWithCustomHTTP.HTTPClient() != customHTTPClient {
+			t.Errorf("Expected custom HTTP client to be set")
+		}
+	})
+}
+
+func TestWithBaseURL(t *testing.T) {
+	t.Run("it should set a custom base URL on the Onsring client", func(t *testing.T) {
+		customBaseURL := "https://custom.onspring.com"
+
+		clientWithCustomURL := onspring.NewClient(
+			"test-api-key",
+			onspring.WithBaseURL(customBaseURL),
+		)
+
+		if clientWithCustomURL.BaseURL() != customBaseURL {
+			t.Errorf("Expected base URL to be %s, got %s", customBaseURL, clientWithCustomURL.BaseURL())
+		}
+	})
+}
+
+func TestWithAPIVersion(t *testing.T) {
+	t.Run("it should set a custom API version on the Onsring client", func(t *testing.T) {
+		customVersion := "3.0"
+
+		clientWithCustomVersion := onspring.NewClient(
+			"test-api-key",
+			onspring.WithAPIVersion(customVersion),
+		)
+
+		if clientWithCustomVersion.APIVersion() != customVersion {
+			t.Errorf("Expected API version to be %s, got %s", customVersion, clientWithCustomVersion.APIVersion())
+		}
+	})
+}