Fix Sonar issue, formatting (#99)

* Fix Sonar issue, formatting

* Remove dev dependencies from requirements.tzt

* Fix unit test failure

app/query_normalisation.py

@@ -3,8 +3,9 @@
 """MODULE: Provides functions that ensure an IP address is
 available to query the APIs for."""
 
-import socket
 import ipaddress
+import socket
+
 import requests
 
 
@@ -17,16 +18,17 @@ def is_ip_address(query: str) -> bool:
         return False
 
 
-def resolve_domain_name(domain_name: str) -> ipaddress.IPv4Address:
+def resolve_domain_name(domain_name: str) -> ipaddress.IPv4Address | None:
     """Resolve a domain name via DNS or return None."""
     try:
-        ip_address = socket.gethostbyname(domain_name)
-    except socket.gaierror:
-        ip_address = None
-    return ip_address
+        result: str = socket.gethostbyname(domain_name)
+        ip_address: ipaddress.IPv4Address = ipaddress.IPv4Address(result)
+        return ip_address
+    except (socket.gaierror, ipaddress.AddressValueError):
+        return None
 
 
 def get_public_ip() -> ipaddress.IPv4Address:
     """Get the user's current public IPv4 address."""
-    ip_address = requests.get("https://api.ipify.org", timeout=10).text
-    return ip_address
+    ip_address: str = requests.get("https://api.ipify.org", timeout=10).text
+    return ipaddress.IPv4Address(ip_address)