Feature/nat 328 site names should be validated

gso/utils/helpers.py

@@ -179,3 +179,18 @@ def validate_country_code(country_code: str) -> str:
         return country_code
     except LookupError:
         raise ValueError("Invalid or non-existent country code, it must be in ISO 3166-1 alpha-2 format.")
+
+
+def validate_site_name(site_name: str) -> str:
+    """Validate the site name.
+
+    The site name must consist of three uppercase letters (A-Z) followed by an optional single digit (0-9).
+    """
+    pattern = re.compile(r"^[A-Z]{3}[0-9]?$")
+    if pattern.match(site_name):
+        return site_name
+    else:
+        raise ValueError(
+            "Enter a valid site name. It must consist of three uppercase letters (A-Z) followed by an optional single "
+            "digit (0-9)."
+        )