Add the API fetcher.

docker_tags_getter/fetcher/api_fetcher.py

@@ -0,0 +1,13 @@
+import requests
+
+class ApiFetcher:
+    """The handler of response."""
+    def __init__(self, config):
+        self.config = config
+
+    def get(self, url) -> (int, dict|None):
+        headers = self.config.get_headers()
+        response = requests.get(url, headers=headers)
+        if response.status_code != 200:
+            return (response.status_code, None)
+        return (response.status_code, response.json())