Description
This PR fixes a issue in the Security Group registration logic where the VNet was being assigned arbitrarily.

1. Before (The Issue)

• When registering a Security Group, the system assigned a random VNetId from any VNet that shared the same Connection Name.

for _, r := range content.VNet {
			if r.ConnectionName == u.ConnectionName {
				u.VNetId = r.Id
			}

• Risk: If multiple VNets existed in the same connection, the Security Group could be linked to the wrong VNet.

2. After ( The Solution)

• Implemented a precise matching logic using the actual CSP data:
  1. Call Spider's /getsecuritygroupowner API using the Security Group's CSP ID.
  2. Retrieve the actual VPC information (NameId, SystemId) from the response.
  3. Search through Tumblebug's registered VNets to find a match for the returned VPC SystemId.
  4. Assign the matched VNet to u.VNetId.
• Error Handling: If no matching VNet is found in Tumblebug, the system now returns a clear error message instead of proceeding with a wrong association.