[REQ] [Java] Preserve the order of model properties by generating @ApiModelProperty.position value

For Java-based generators, @ApiModelProperty has a position property that can be used for implementors to sort model properties, like what has been done in Springfox Swagger2.

Without the position property value generated for the Java accessor method, the only reliable way to ensure the property order constant from run to run is to sort the properties by its name due to the limitation of Class.getDeclaredMethods(). And this behavior may results inconsistent to the OAI definition.

Describe the solution you'd like

Add config option like preserveModelPropertiesOrder to all generators which generating Swagger Annotation. For best compatibility, the default of this property should be false.

However, there exist sortModelPropertiesByRequiredFlag option may inference with this proposed option.

Start by reviewing the Java-based generators that produce Swagger annotations and the existing sortModelPropertiesByRequiredFlag option. Compare the requested preserveModelPropertiesOrder behavior with the Springfox example and determine how the two options should interact. Done means the option is consistently supported by the relevant generators and generated model properties receive the expected positions.