Allow proper setCount SLAs across zones (#8752)

Fixes scenario where zones are appropriately
handled, along with supporting overriding set
count. The new fix also ensures that we handle
the various setup types properly.

Update documentation to properly indicate the
behavior.

Fixes #8750

Co-authored-by: Nitish Tiwari <nitish@minio.io>

cmd/endpoint.go

@@ -194,6 +194,24 @@ type ZoneEndpoints struct {
 // EndpointZones - list of list of endpoints
 type EndpointZones []ZoneEndpoints
 
+// Add add zone endpoints
+func (l *EndpointZones) Add(zeps ZoneEndpoints) error {
+	existSet := set.NewStringSet()
+	for _, zep := range *l {
+		for _, ep := range zep.Endpoints {
+			existSet.Add(ep.String())
+		}
+	}
+	// Validate if there are duplicate endpoints across zones
+	for _, ep := range zeps.Endpoints {
+		if existSet.Contains(ep.String()) {
+			return fmt.Errorf("duplicate endpoints found")
+		}
+	}
+	*l = append(*l, zeps)
+	return nil
+}
+
 // FirstLocal returns true if the first endpoint is local.
 func (l EndpointZones) FirstLocal() bool {
 	return l[0].Endpoints[0].IsLocal
@@ -608,13 +626,14 @@ func CreateEndpoints(serverAddr string, foundLocal bool, args ...[]string) (Endp
 
 	// All endpoints are pointing to local host
 	if len(endpoints) == localEndpointCount {
-		// If all endpoints have same port number, then this is XL setup using URL style endpoints.
+		// If all endpoints have same port number, Just treat it as distXL setup
+		// using URL style endpoints.
 		if len(localPortSet) == 1 {
 			if len(localServerHostSet) > 1 {
 				return endpoints, setupType,
 					config.ErrInvalidErasureEndpoints(nil).Msg("all local endpoints should not have different hostnames/ips")
 			}
-			return endpoints, XLSetupType, nil
+			return endpoints, DistXLSetupType, nil
 		}
 
 		// Even though all endpoints are local, but those endpoints use different ports.