Add API documentation and migration guide - Add detailed API documentation for Go packages - Create migration guide for users transitioning from Bash to Go

Author: JohanDevl

docs/API.md

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+# API Documentation
+
+This document provides an overview of the packages and APIs available in the Go implementation of Export_Trakt_4_Letterboxd.
+
+## Package Structure
+
+The application is organized into the following packages:
+
+```
+/cmd
+  /export_trakt     - Main application entry point
+/pkg
+  /api             - Trakt.tv API client
+  /config          - Configuration loading and validation
+  /export          - Letterboxd export functionality
+  /i18n            - Internationalization support
+  /logger          - Logging system
+```
+
+## Config Package
+
+The `config` package handles loading, parsing, and validating application configuration from TOML files.
+
+### Types
+
+#### `Config`
+
+The main configuration structure that contains all configuration options.
+
+```go
+type Config struct {
+    Trakt     TraktConfig     `toml:"trakt"`
+    Letterboxd LetterboxdConfig `toml:"letterboxd"`
+    Export    ExportConfig    `toml:"export"`
+    Logging   LoggingConfig   `toml:"logging"`
+    I18n      I18nConfig      `toml:"i18n"`
+}
+```
+
+### Functions
+
+#### `LoadConfig`
+
+```go
+func LoadConfig(path string) (*Config, error)
+```
+
+Loads and parses a TOML configuration file from the specified path.
+
+#### `Validate`
+
+```go
+func (c *Config) Validate() error
+```
+
+Validates that the configuration meets all requirements.
+
+## Logger Package
+
+The `logger` package provides a flexible logging system with support for different output targets and log levels.
+
+### Interfaces
+
+#### `Logger`
+
+```go
+type Logger interface {
+    Info(messageID string, data ...map[string]interface{})
+    Infof(messageID string, data map[string]interface{})
+    Error(messageID string, data ...map[string]interface{})
+    Errorf(messageID string, data map[string]interface{})
+    Warn(messageID string, data ...map[string]interface{})
+    Warnf(messageID string, data map[string]interface{})
+    Debug(messageID string, data ...map[string]interface{})
+    Debugf(messageID string, data map[string]interface{})
+    SetLogLevel(level string)
+    SetLogFile(path string) error
+    SetTranslator(t Translator)
+}
+```
+
+#### `Translator`
+
+```go
+type Translator interface {
+    Translate(messageID string, templateData map[string]interface{}) string
+}
+```
+
+### Functions
+
+#### `NewLogger`
+
+```go
+func NewLogger() Logger
+```
+
+Creates a new logger instance with default settings.
+
+## API Package
+
+The `api` package handles communication with the Trakt.tv API.
+
+### Types
+
+#### `Client`
+
+The main client for interacting with the Trakt.tv API.
+
+```go
+type Client struct {
+    // private fields
+}
+```
+
+#### `Movie`
+
+```go
+type Movie struct {
+    Movie         MovieInfo `json:"movie"`
+    LastWatchedAt string    `json:"last_watched_at,omitempty"`
+    Rating        float64   `json:"rating,omitempty"`
+}
+```
+
+### Functions
+
+#### `NewClient`
+
+```go
+func NewClient(cfg *config.Config, log logger.Logger) *Client
+```
+
+Creates a new Trakt API client.
+
+#### `GetWatchedMovies`
+
+```go
+func (c *Client) GetWatchedMovies() ([]Movie, error)
+```
+
+Retrieves the list of watched movies from Trakt.tv.
+
+## Export Package
+
+The `export` package provides functionality for exporting data to Letterboxd format.
+
+### Types
+
+#### `LetterboxdExporter`
+
+```go
+type LetterboxdExporter struct {
+    // private fields
+}
+```
+
+### Functions
+
+#### `NewLetterboxdExporter`
+
+```go
+func NewLetterboxdExporter(cfg *config.Config, log logger.Logger) *LetterboxdExporter
+```
+
+Creates a new Letterboxd exporter.
+
+#### `ExportMovies`
+
+```go
+func (e *LetterboxdExporter) ExportMovies(movies []api.Movie) error
+```
+
+Exports a list of movies to Letterboxd CSV format.
+
+## i18n Package
+
+The `i18n` package handles internationalization and localization.
+
+### Types
+
+#### `Translator`
+
+```go
+type Translator struct {
+    // private fields
+}
+```
+
+### Functions
+
+#### `NewTranslator`
+
+```go
+func NewTranslator(cfg *config.I18nConfig, log logger.Logger) (*Translator, error)
+```
+
+Creates a new translator instance.
+
+#### `Translate`
+
+```go
+func (t *Translator) Translate(messageID string, templateData map[string]interface{}) string
+```
+
+Returns the translated message for the given message ID.
+
+#### `SetLanguage`
+
+```go
+func (t *Translator) SetLanguage(lang string)
+```
+
+Changes the current language for the translator.
+
+## Example Usage
+
+### Loading Configuration
+
+```go
+cfg, err := config.LoadConfig("config/config.toml")
+if err != nil {
+    log.Fatalf("Failed to load configuration: %v", err)
+}
+```
+
+### Setting Up Logging
+
+```go
+log := logger.NewLogger()
+log.SetLogLevel(cfg.Logging.Level)
+if cfg.Logging.File != "" {
+    if err := log.SetLogFile(cfg.Logging.File); err != nil {
+        log.Errorf("Failed to set log file: %v", err)
+    }
+}
+```
+
+### Using the API Client
+
+```go
+client := api.NewClient(cfg, log)
+movies, err := client.GetWatchedMovies()
+if err != nil {
+    log.Errorf("Failed to get watched movies: %v", err)
+    return
+}
+```
+
+### Exporting Data
+
+```go
+exporter := export.NewLetterboxdExporter(cfg, log)
+if err := exporter.ExportMovies(movies); err != nil {
+    log.Errorf("Failed to export movies: %v", err)
+    return
+}
+```
+
+### Internationalization
+
+```go
+translator, err := i18n.NewTranslator(&cfg.I18n, log)
+if err != nil {
+    log.Errorf("Failed to initialize translator: %v", err)
+    return
+}
+
+// Set translator for logger
+log.SetTranslator(translator)
+
+// Log with translation
+log.Info("app.starting", map[string]interface{}{"version": "1.0.0"})
+
+// Get translated message
+message := translator.Translate("app.welcome", nil)
+fmt.Println(message)
+```