[Java] [typescript-angular] Bug swagger-codegen Invalid output for methods with URL Query parameters

Description

Swagger Codegen produces incorrect output for typescript-angular for get methods that receive multiple query parameters (?a=1&b=2). But produces the correct output for get methods that receive path parameters (/{a}/{b} /1/2 )

/**
     * getDocumentTypes
     * 
     * @param documentContext documentContext
     * @param lifecycleStage lifecycleStage
     * @param processType processType
     * @param observe set whether or not to return the data Observable as the body, response or events. defaults to returning the body.
     * @param reportProgress flag to report request and response progress.
     */
    public getDocumentTypesUsingGET(documentContext?: string, lifecycleStage?: string, processType?: string, observe?: 'body', reportProgress?: boolean): Observable<ResponseGenericListDocumentSubType>;
    public getDocumentTypesUsingGET(documentContext?: string, lifecycleStage?: string, processType?: string, observe?: 'response', reportProgress?: boolean): Observable<HttpResponse<ResponseGenericListDocumentSubType>>;
    public getDocumentTypesUsingGET(documentContext?: string, lifecycleStage?: string, processType?: string, observe?: 'events', reportProgress?: boolean): Observable<HttpEvent<ResponseGenericListDocumentSubType>>;
    public getDocumentTypesUsingGET(documentContext?: string, lifecycleStage?: string, processType?: string, observe: any = 'body', reportProgress: boolean = false ): Observable<any> {
    
        let queryParameters = new HttpParams({encoder: new CustomHttpUrlEncodingCodec()});
        if (documentContext !== undefined && documentContext !== null) {
            queryParameters = queryParameters.set('documentContext', <any>documentContext);
        }
        if (lifecycleStage !== undefined && lifecycleStage !== null) {
            queryParameters = queryParameters.set('lifecycleStage', <any>lifecycleStage);
        }
        if (processType !== undefined && processType !== null) {
            queryParameters = queryParameters.set('processType', <any>processType);
        }

        let headers = this.defaultHeaders;

        // to determine the Accept header
        let httpHeaderAccepts: string[] = [
            '*/*'
        ];
        const httpHeaderAcceptSelected: string | undefined = this.configuration.selectHeaderAccept(httpHeaderAccepts);
        if (httpHeaderAcceptSelected != undefined) {
            headers = headers.set('Accept', httpHeaderAcceptSelected);
        }

        // to determine the Content-Type header
        const consumes: string[] = [
            'application/json'
        ];

// ERROR ON THIS LINE
        return this.httpClient.get<ResponseGenericListDocumentSubType>(`${this.basePath}/adr/refData/documentTypes${encodeURIComponent(String(documentContextlifecycleStageprocessType))}`,
            {
                params: queryParameters,
                withCredentials: this.configuration.withCredentials,
                headers: headers,
                observe: observe,
                reportProgress: reportProgress
            }
        );
    }

The url query parameters are incorrectly appended and encoded at the end of the url path

return this.httpClient.get<ResponseGenericListDocumentSubType>
(`${this.basePath}/adr/refData/documentTypes${encodeURIComponent(String(documentContextlifecycleStageprocessType))}`,

Swagger-codegen version

swagger-codegen-cli-2.3.1

Swagger declaration file content or url

"/adr/refData/documentTypes{?documentContext,lifecycleStage,processType}": {
            "get": {
                "tags": [
                    "adr-reference-data-controller"
                ],
                "summary": "getDocumentTypes",
                "operationId": "getDocumentTypesUsingGET",
                "consumes": [
                    "application/json"
                ],
                "produces": [
                    "*/*"
                ],
                "parameters": [
                    {
                        "name": "documentContext",
                        "in": "query",
                        "description": "documentContext",
                        "required": false,
                        "type": "string"
                    },
                    {
                        "name": "lifecycleStage",
                        "in": "query",
                        "description": "lifecycleStage",
                        "required": false,
                        "type": "string"
                    },
                    {
                        "name": "processType",
                        "in": "query",
                        "description": "processType",
                        "required": false,
                        "type": "string"
                    }
                ],
                "responses": {
                    "200": {
                        "description": "OK",
                        "schema": {
                            "$ref": "#/definitions/ResponseGeneric«List«DocumentSubType»»"
                        }
                    },
                    "401": {
                        "description": "Unauthorized"
                    },
                    "403": {
                        "description": "Forbidden"
                    },
                    "404": {
                        "description": "Not Found"
                    }
                }
            }
        },

Command line used for generation

java -jar tools/swagger-codegen-cli-2.3.1.jar generate -i http://localhost:8082/ngs/swagger.json -l typescript-angular -t tools/templates -o src/app/api -c swagger-codegen.config.json

Steps to reproduce

Related issues/PRs

Suggest a fix/enhancement

I would guess the error resides somewhere in since the {{{path}}} is output as in Mustache templates

https://github.com/swagger-api/swagger-codegen/blob/v2.3.1/modules/swagger-codegen/src/main/java/io/swagger/codegen/languages/TypeScriptAngularClientCodegen.java

Start with TypeScriptAngularClientCodegen.java and the Mustache template usage referenced by {{{path}}}; reproduce generation with the supplied swagger-codegen command and OpenAPI path. Trace why query parameters are included in the encoded path, then verify generated typescript-angular methods keep them in the HttpParams request options rather than appending them to the URL.