Add error handling

Sources/ResgenSwift/Analytics/AnalyticsError.swift

@@ -0,0 +1,32 @@
+//
+//  AnalyticsError.swift
+//
+//
+//  Created by Loris Perret on 11/12/2023.
+//
+
+import Foundation
+
+enum AnalyticsError: Error {
+    case fileNotExists(String)
+    case missingElement(String)
+    case invalidParameter(String)
+    
+    case writeFile(String, String)
+    
+    var description: String {
+        switch self {
+        case .fileNotExists(let filename):
+            return "error: [\(Analytics.toolName)] File \(filename) does not exists "
+            
+        case .missingElement(let element):
+            return "error: [\(Analytics.toolName)] Missing \(element) for Matomo"
+            
+        case .invalidParameter(let reason):
+            return "error: [\(Analytics.toolName)] Invalid parameter \(reason)"
+            
+        case .writeFile(let subErrorDescription, let filename):
+            return "error: [\(Analytics.toolName)] An error occured while writing content to \(filename): \(subErrorDescription)"
+        }
+    }
+}