to add Swagger generated API documentation, I do:
		
		
		A) add this dependency to the project pom.xml
			<dependency>
				<groupId>org.springdoc</groupId>
				<artifactId>springdoc-openapi-starter-webmvc-ui</artifactId>
				<version>2.0.3</version>
			</dependency>
		
		B) open a Browser to:
		    http://localhost:9091/swagger-ui/index.html
		    
		    
	    To see the actual Open-Api data use this URL:
	    http://localhost:9091/v3/api-docs (JSON format)
	    http://localhost:9091/v3/api-docs.yaml (YAML format)
	    
	    
	    I can customize the generated documentation by adding Open-API annotations tot my RestController
	    
		@Operation(summary = "Get a specific Route by Route Code")
		@ApiResponses(value = { 
		  @ApiResponse(responseCode = "200", description = "Found the Route", 
		    content = { @Content(mediaType = "application/json", 
		      schema = @Schema(implementation = Route.class)) }),
		  @ApiResponse(responseCode = "400", description = "Invalid code format", 
		    content = @Content), 
		  @ApiResponse(responseCode = "404", description = "Route not found", 
		    content = @Content) })
		@GetMapping(value="/route/{code}", produces="application/json")
		Route getRouteByCode(@PathVariable String code)  throws IOException;

	   and my implementation has this code:

		@Override
		public Route getRouteByCode(String code) throws IOException {
			if (code.length() < 2) {
				throw new ResponseStatusException(HttpStatus.BAD_REQUEST, "The code must be at least 2 chars in length");
			}
			Route route = routeService.getRouteByCode(code);
			if (route == null) {
				throw new ResponseStatusException(HttpStatus.NOT_FOUND, "The route cannot be found");
			}
			return route;
		}
		
		
	I you would like your Message included in the HttpResponse error, you add this to the application.properties file
	    
	    server.error.include-message=always