[management] Add option to disable default all-to-all policy (#3970)

This PR introduces a new configuration option `DisableDefaultPolicy` that prevents the creation of the default all-to-all policy when new accounts are created. This is useful for automation scenarios where explicit policies are preferred.
### Key Changes:
- Added DisableDefaultPolicy flag to the management server config
- Modified account creation logic to respect this flag
- Updated all test cases to explicitly pass the flag (defaulting to false to maintain backward compatibility)
- Propagated the flag through the account manager initialization chain

### Testing:

- Verified default behavior remains unchanged when flag is false
- Confirmed no default policy is created when flag is true
- All existing tests pass with the new parameter

management/server/types/account.go

@@ -1546,7 +1546,7 @@ func getPoliciesSourcePeers(policies []*Policy, groups map[string]*Group) map[st
 }
 
 // AddAllGroup to account object if it doesn't exist
-func (a *Account) AddAllGroup() error {
+func (a *Account) AddAllGroup(disableDefaultPolicy bool) error {
 	if len(a.Groups) == 0 {
 		allGroup := &Group{
 			ID:     xid.New().String(),
@@ -1558,6 +1558,10 @@ func (a *Account) AddAllGroup() error {
 		}
 		a.Groups = map[string]*Group{allGroup.ID: allGroup}
 
+		if disableDefaultPolicy {
+			return nil
+		}
+
 		id := xid.New().String()
 
 		defaultPolicy := &Policy{

management/server/types/config.go

@@ -53,6 +53,9 @@ type Config struct {
 	StoreConfig StoreConfig
 
 	ReverseProxy ReverseProxy
+	
+	// disable default all-to-all policy
+	DisableDefaultPolicy bool
 }
 
 // GetAuthAudiences returns the audience from the http config and device authorization flow config