Feature/nat 328 site names should be validated

gso/api/v1/imports.py

 import ipaddress
+import re
 from typing import Any
 from uuid import UUID
 
@@ -38,6 +39,15 @@ class SiteImportModel(BaseModel):
     site_ts_address: str
     customer: str
 
+    @validator("site_name", allow_reuse=True)
+    def site_name_must_be_valid(cls, site_name: str) -> str:
+        # Accept 3 chapital letters and only one ditigt after capital letters.
+        pattern = re.compile(r"^[A-Z]{3}[0-9]?$")
+        if not bool(pattern.match(site_name)):
+            raise ValueError(f"Enter a valid site name similar looks like AMS, AMS1or LON9. Get: {site_name}")
+
+        return site_name
+
 
 class RouterImportModel(BaseModel):
     customer: str