New handlers: refactored, Web API and AWS Lambda support

[witoszekdev]

Description

This PR introduces new handlers for Fetch Web API and AWS Lambda and refactors existing code so that it can easily allow adding new platforms in the future.

After the change handlers code is splits them into 3 parts:

1. Platform Adapter - class that is responsible of:
   • parsing received requests from specific platform format (e.g. Next.js request, Web API Request) into a common format
   • and preparing response from common format into platform specific format (e.g. Next.js response, Web API Response)
2. Handler use cases - class that represents business logic specific to handler, has a single method that returns a result
   • e.g. register use case: readers all required headers from request, validates it, saves to apl, returns success or failure
3. Handler factory method - function that creates a handler instance with all dependencies injected, each platform has separate folder, for example:
   • src/handlers/nextjs - For handlers that use Next.js platform adapter
   • src/handlers/fetch-api - For handlers that use Fetch API platform adapter

This way we'll be able to easily add new platforms and handlers without changing existing code.

Currently in this PR:

• Next.js - existing implementation, shouldn't be changed
• Web API - new implementation
• AWS Lambda event - new implementation

Breaking changes

SaleorWebhook accepts onError and formatErrorResponse parameters callbacks, now they won't pass res object in Next.js runtime, since these methods weren't supposed to send responses

[changeset-bot]

🦋 Changeset detected

Latest commit: 6712040

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 1 package

Name	Type
@saleor/app-sdk	Minor

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[github-actions]

Package	Line Rate	Branch Rate	Complexity	Health
src	74%	93%	0	➖
src.APL	85%	85%	0	✔
src.APL.saleor-cloud	75%	86%	0	✔
src.APL.vercel-kv	54%	69%	0	➖
src.app-bridge	88%	86%	0	✔
src.handlers.next	93%	86%	0	✔
src.handlers.next.saleor-webhooks	91%	78%	0	✔
src.handlers.shared	90%	76%	0	✔
src.middleware	98%	97%	0	✔
src.settings-manager	96%	89%	0	✔
src.test-utils	100%	90%	0	✔
src.util	82%	100%	0	✔
Summary	85% (4081 / 4775)	85% (485 / 569)	0	✔

[lkostrowski]

It would be easier for me to review if I already see docs with examples. In case of SDK public API is more important than the code

[lkostrowski]

please make it major since it has breaking changes

[lkostrowski]

please remember to add full changeset and docs

[lkostrowski]

won't it have the same names as fetch api? It would be confusing, probably better to also add alias on export

so next-app-router file can include export { FetchApi as NextAppRouterWebhook } from '../fetch-api' or something like this

[lkostrowski]

would be easier if we see docs at this point