Fix type of x_ssh_keys

The `unifi_settings_mgmt` resource fails for me with the following error:

```
Error: unable to decode body: GET s/default/get/setting/mgmt unable to unmarshal alias: json: cannot unmarshal object into Go struct field .x_ssh_keys of type string
```

My `x_ssh_keys` looks like this:

```
[
  {
    "name": "Laptop",
    "type": "ssh-rsa",
    "key": "REDACTED",
    "comment": "REDACTED",
    "date": "2021-02-25T08:26:04Z",
    "fingerprint": "REDACTED"
  }
]
```

fields/main.go

@@ -306,6 +306,24 @@ func main() {
 				f.OmitEmpty = true
 				return nil
 			}
+		case "SettingMgmt":
+			sshKeyField := NewFieldInfo(resource.StructName+"XSshKeys", "x_ssh_keys", "struct", "", false, false)
+			sshKeyField.Fields = map[string]*FieldInfo{
+				"name":        NewFieldInfo("name", "name", "string", "", false, false),
+				"keyType":     NewFieldInfo("keyType", "type", "string", "", false, false),
+				"key":         NewFieldInfo("key", "key", "string", "", false, false),
+				"comment":     NewFieldInfo("comment", "comment", "string", "", false, false),
+				"date":        NewFieldInfo("date", "date", "string", "", false, false),
+				"fingerprint": NewFieldInfo("fingerprint", "fingerprint", "string", "", false, false),
+			}
+			resource.Types[sshKeyField.FieldName] = sshKeyField
+
+			resource.FieldProcessor = func(name string, f *FieldInfo) error {
+				if name == "XSshKeys" {
+					f.FieldType = sshKeyField.FieldName
+				}
+				return nil
+			}
 		case "SettingUsg":
 			resource.FieldProcessor = func(name string, f *FieldInfo) error {
 				if strings.HasSuffix(name, "Timeout") && name != "ArpCacheTimeout" {