Feature/update input form validation

Update the input forms for site and router creation.

Changes:

• Site country code must exist
• TS server address must be valid
• Router TS port must be valid
• Site latitude and longitude must make sense (-90 < x < 90 and -180 < y < 180)

gso/products/product_blocks/router.py

@@ -78,7 +78,7 @@ class RouterBlock(RouterBlockProvisioning, lifecycle=[SubscriptionLifecycle.ACTI
     router_fqdn: str
     """{term}`FQDN` of a router."""
     router_ts_port: PortNumber
-    """The port of the terminal server that this router is connected to. Used to provide out of band access."""
+    """The port of the terminal server that this router is connected to. Used to offer out of band access."""
     router_access_via_ts: bool
     """Whether this router should be accessed through the terminal server, or through its loopback address."""
     router_lo_ipv4_address: ipaddress.IPv4Address