Add initial implementation of *arr service client

- Created `client.go` for the main client structure and methods to interact with *arr services.
- Added `types.go` to define data structures for system status, movies, and series.
- Implemented `radarr.go` for Radarr-specific client methods including health checks and movie retrieval.
- Introduced `interfaces.go` to define service interfaces for common operations across *arr services.
- Established a basic `main.go` for application entry point.
- Included a tutorial markdown file to guide users through building the client and understanding Go concepts.
- Initialized `go.mod` for module management.
- Organized code into appropriate packages for better structure and maintainability.

interfaces.go

@@ -0,0 +1,30 @@
+package main
+
+// ServiceClient defines the interface all *arr services must implement
+type ServiceClient interface {
+	GetSystemStatus() (*SystemStatus, error)
+	GetHealth() ([]HealthCheck, error)
+}
+
+// MovieService defines movie-specific operations (Radarr)
+type MovieService interface {
+	ServiceClient
+	GetMovies() ([]Movie, error)
+	GetMovie(id int) (*Movie, error)
+	AddMovie(movie *Movie) (*Movie, error)
+}
+
+// SeriesService defines series-specific operations (Sonarr)
+type SeriesService interface {
+	ServiceClient
+	GetSeries() ([]Series, error)
+	GetSeriesById(id int) (*Series, error)
+	AddSeries(series *Series) (*Series, error)
+}
+
+// HealthCheck is the struct that represents the health check result.
+type HealthCheck struct {
+	Source  string `json:"source"`
+	Type    string `json:"type"`
+	Message string `json:"message"`
+}