fix(discovery): support NestJS 11

[xballoy]

Fix #937 to support NestJS 11.

Starting version 11, InstanceWrapper.inject can be null (see v11 vs v10).

In order to prevent a breaking change in discovery by respecting the DiscoveredClass type we map null to undefined.

Fixes #944

[xballoy]

I successfully locally run

pnpm build --concurrency=12 
pnpm test:ci
pnpm test:vitest:ci

I did not run the pnpm test:ci:integration because I don't want to setup a local RabbitMQ but this package is not impacted anyway.

[underfisk]

I successfully locally run

pnpm build --concurrency=12 
pnpm test:ci
pnpm test:vitest:ci

I did not run the pnpm test:ci:integration because I don't want to setup a local RabbitMQ but this package is not impacted anyway.

@xballoy Not an issue, CI will run those checks for you.

[underfisk]

lgtm thank you