Error if resources.extensions contains reference to not created resource

[medikoo]

Use case description

Currently we silently accept an extension to not existing resource. Ideally we should throw in such case

Proposed solution

1. In master branch

Configure deprecation to be shown at:

serverless/lib/plugins/aws/package/lib/mergeCustomProviderResources.js

Line 33 in 5f85543

template.Resources[resourceName] = {};

Addressed with #8266

2. In v{nextMajor} branch

Should be implemented after v{nextMajor} branch is created and (1) is merged to master and v{nextMajor} branch

Replace configured deprecation (leaving its documentation entry), with thrown error

[pgrzesik]

Hello 👋 I'm wondering, with v2 being close to be released, should that deprecation be introduced for v2 or to current master? I feel like it might be a short period of time for people to actually see the deprecation before it starts breaking for them in new version. What is your opinion on that?

[medikoo]

@pgrzesik thanks for asking. I would work against master. If in a meantime v2 will get released then it'll automatically will be merged to master so automatically this PR will catch up. If on other hand we merge it to master before releasing v2, then we will have to implement (2) step in v2 before releasing it (and imo that's fine!)

[medikoo]

Still, it's definitely not blocking for v2, otherwise it'll be marked with v2 milestone

[medikoo]

Addressed with #10063