Cleanup `OpenFgaApi` code base

[rhamzeh]

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Describe the problem you'd like to have solved

The code base in https://github.com/openfga/js-sdk/blob/main/api.ts is too convoluted, it has many unnecessary abstractions and lots of repeated code that can be cleaned up.

[Siddhant-K-code]

Hi @rhamzeh, I've looked into the cleanup task for api.ts and found that this file is auto-generated by OpenAPI Generator from our API specification. So, not sure how we can clean up that directly as it will be regenerated again.

I am not sure, where to find our OpenAPI Generator.

[ewanharris]

👋🏻 Our generation pieces (SDK templates, scripts etc.) live in the openfga/sdk-generator repo.

The code being referred to is specifically in the js template in the apiInner.mustache file.

I'm not sure if @rhamzeh is thinking the same as myself, but I think we can potentially do away with everything in there except the OpenFgaApi class, folding things like parameter assertions (template), request building (template), and request/telemetry creation (template) into the class methods directly as opposed to how they're currently spread across different methods

[rhamzeh]

To elaborate on what @ewanharris said:

Some concerns of mine:

• We have the methods in the OpenFgaApi, e.g.

  js-sdk/api.ts

  Lines 1216 to 1218 in 006b5c4

  	public check(storeId: string, body: CheckRequest, options?: any): Promise<CallResult<CheckResponse>> {
  	return OpenFgaApiFp(this.configuration, this.credentials).check(storeId, body, options).then((request) => request(this.axios));
  	}

  that just call other implementations, but no one uses those, the implementation should be moved here and the methods dropped.
• Many methods have duplicate code. e.g. this section or something similar

  js-sdk/api.ts

  Lines 587 to 623 in 006b5c4

  	// verify required parameter 'storeId' is not null or undefined
  	assertParamExists("readChanges", "storeId", storeId);
  	const localVarPath = "/stores/{store_id}/changes"
  	.replace(`{${"store_id"}}`, encodeURIComponent(String(storeId)));
  	// use dummy base URL string because the URL constructor only accepts absolute URLs.
  	const localVarUrlObj = new URL(localVarPath, DUMMY_BASE_URL);
  	let baseOptions;
  	if (configuration) {
  	baseOptions = configuration.baseOptions;
  	}
  	const localVarRequestOptions = { method: "GET", ...baseOptions, ...options};
  	const localVarHeaderParameter = {} as any;
  	const localVarQueryParameter = {} as any;
  	if (type !== undefined) {
  	localVarQueryParameter["type"] = type;
  	}
  	if (pageSize !== undefined) {
  	localVarQueryParameter["page_size"] = pageSize;
  	}
  	if (continuationToken !== undefined) {
  	localVarQueryParameter["continuation_token"] = continuationToken;
  	}
  	if (startTime !== undefined) {
  	localVarQueryParameter["start_time"] = (startTime as any instanceof Date) ?
  	(startTime as any).toISOString() :
  	startTime;
  	}
  	setSearchParams(localVarUrlObj, localVarQueryParameter, options.query);
  	localVarRequestOptions.headers = {...localVarHeaderParameter, ...options.headers};

  is implemented for each method. We should have a common function that takes any specifics and returns the relevant data - we can pass in the required attributes, what the method is, etc..

The template for this file currently lives in https://github.com/openfga/sdk-generator/blob/main/config/clients/js/template/apiInner.mustache