WIP http client

Roughly based on the Amtraker node library so this and the models will eventually be spun off as one too

Sources/AmtrakStatus/AmtrakClient.swift

@@ -0,0 +1,34 @@
+import Foundation
+
+enum AmtrakError: Error {
+    case invalidURL(String)
+    case invalidResponse
+    case httpStatus(Int)
+    case stationNotFound(String)
+}
+
+struct AmtrakClient {
+    var decoder = JSONDecoder()
+    
+    let stationBaseURL = "https://api.amtraker.com/v3/stations"
+    let trainsBaseURL =  "https://api.amtraker.com/v3/trains"
+    let staleBaseURL = "https://api.amtraker.com/v3/stale"
+    
+    func get<T: Decodable>(_ urlString: String) async throws -> T {
+        
+        guard let url = URL(string: urlString) else {
+            throw AmtrakError.invalidURL(urlString)
+        }
+        
+        let (data, reponse) = try await URLSession.shared.data(from: url)
+        guard let http = reponse as? HTTPURLResponse else {
+            throw AmtrakError.invalidResponse
+        }
+        
+        guard (200..<300).contains(http.statusCode) else {
+            throw AmtrakError.httpStatus(http.statusCode)
+        }
+        
+        return try decoder.decode(T.self, from: data)
+    }
+}