feat: load application and repository configuration from env and TOML

Services/AppConfig.cs

@@ -0,0 +1,52 @@
+using DotNetEnv;
+
+namespace ForgejoReleaseSync.Services;
+
+public class AppConfig
+{
+    public required string ForgejoInstacne { get; set; }
+    public required string ForgejoToken { get; set; }
+    public required ushort SyncConcurrency { get; set; }
+    public required string RepositoryConfigFilePath  { get; set; }
+}
+
+
+public static class AppConfigLoader
+{
+    public static AppConfig LoadConfigFromEnv()
+    {
+        Env.Load();
+
+        var forgejoInstance = Environment.GetEnvironmentVariable("FORGEJO_INSTANCE");
+        var forgejoToken = Environment.GetEnvironmentVariable("FORGEJO_TOKEN");
+        var syncConcurrency = Environment.GetEnvironmentVariable("SYNC_CONCURRENCY");
+        var repoConfigFilePath = Environment.GetEnvironmentVariable("REPO_CONFIG_FILE");
+
+        if (string.IsNullOrEmpty(forgejoInstance))
+            throw new Exception("FORGEJO_INSTANCE environment variable is required");
+        if (!string.IsNullOrEmpty(forgejoToken) && forgejoInstance.EndsWith('/'))
+            forgejoInstance = forgejoInstance[..^1];
+
+        if (string.IsNullOrEmpty(forgejoToken))
+            throw new Exception("FORGEJO_TOKEN environment variable is required");
+
+        ushort syncConcurrencyParsed = 3;
+        if (!string.IsNullOrEmpty(syncConcurrency))
+            ushort.TryParse(syncConcurrency, out syncConcurrencyParsed);
+        if (syncConcurrencyParsed > 10)
+            throw new ArgumentOutOfRangeException(nameof(syncConcurrencyParsed),
+                "Sync concurrency cannot be greater than 10");
+        
+        if (string.IsNullOrEmpty(repoConfigFilePath))
+            throw new Exception("REPO_CONFIG_FILE environment variable is required");        
+
+
+        return new AppConfig
+        {
+            ForgejoInstacne =  forgejoInstance,
+            ForgejoToken = forgejoToken,
+            SyncConcurrency = syncConcurrencyParsed,
+            RepositoryConfigFilePath =  repoConfigFilePath
+        };
+    }
+}