Way to connect user pool to authenticate and access lambda

### Is this feature request related to a new or existing Amplify category?

api

### Is this related to another service?

No

### Describe the feature you'd like to request

From Amazon customer via support:
I have passed auth part and now trying to connect api to this amplify. I added it using amplify add api and amplify update api to update the existing ones.

I don't want to create a new lambda. I want to add my old api to this amplify. Neither update or add give me the choice. I saw in the document to update the amplifyconfiguration.json file. But changing that file doesn't change our amplify settings in cloud.

### Describe the solution you'd like

I want, to use amplify update api to add more api gateway endpoints. I have things like POST /user/collection/add, POST /user/collection, DELETE /user/anotherthing/remove, POST /user/anotherthing/add. When I set it up, I attached it to a lambda that was generated during the first amplify add api. After that, I would go to apigateway and change those to point to correct lambdas which I had already implemented ahead of time. But every time I add/update/change amplify and push, apigateway settings go back to the dummy lambda from the first step and all my other lambdas are gone. How can I avoid overriding it?

### Describe alternatives you've considered

No alternatives

### Additional context

SIM:V541384884

### Is this something that you'd be interested in working on?

- [ ] 👋 I may be able to implement this feature request

### Would this feature include a breaking change?

- [ ] ⚠️ This feature might incur a breaking change