feat(api): add basic auth support

pkg/gotenberg/env.go

@@ -0,0 +1,35 @@
+package gotenberg
+
+import (
+	"fmt"
+	"os"
+	"strconv"
+)
+
+// StringEnv retrieves the value of the environment variable named by the key.
+// If the variable is present in the environment and not empty, the value is
+// returned.
+func StringEnv(key string) (string, error) {
+	val, ok := os.LookupEnv(key)
+	if !ok {
+		return "", fmt.Errorf("environment variable '%s' does not exist", key)
+	}
+	if val == "" {
+		return "", fmt.Errorf("environment variable '%s' is empty", key)
+	}
+	return val, nil
+}
+
+// IntEnv relies on [StringEnv] and converts the values if it exists and is not
+// empty.
+func IntEnv(key string) (int, error) {
+	val, err := StringEnv(key)
+	if err != nil {
+		return 0, err
+	}
+	intVal, err := strconv.Atoi(val)
+	if err != nil {
+		return 0, fmt.Errorf("get int value of environment variable '%s': %w", key, err)
+	}
+	return intVal, nil
+}