978: remove spring-web

Ticket: planning#978 (closed)

• removed dependency
• added OkHttpClient
• created intermediate client to abstract between logic and HTTP handling
• adjusted and extended tests

api/src/main/java/dev/fitko/fitconnect/api/exceptions/RestApiException.java

@@ -2,7 +2,7 @@ package dev.fitko.fitconnect.api.exceptions;
 
 public class RestApiException extends RuntimeException {
 
-    private int statusCode = 400;
+    private int statusCode = 500;
 
     public RestApiException(final String errorMessage, final Throwable error) {
         super(errorMessage, error);