Add AsyncLocalStorage driver

[Aareksio]

So I decided to spent the day implementing AsyncLocalStorage driver... Resolves https://github.com/Aliheym/typeorm-transactional/issues/22

The PR is best read commit after commit, as I tried to make incremental changes:

• implemented StorageDriver abstraction layer to use the adapter / strategy pattern
• implemented cls-hooked driver, all tests green
• implemented AsyncLocalStorage driver, all tests green
• added storageDriver option, defaults to cls-hooked
• added TEST_STORAGE_DRIVER env variable to use different driver in tests

Need to figure out a way to test both drivers on the same suite. It seems infeasible to copy-and-paste cases, or worse prepare some specific cases for drivers. Best to run everything twice to ensure 100% combability. The lib sadly stores some information in memory (eg. dataSources map) and there is currently no way to clean it up between runs, so .each fails. Therefore I temporarily added TEST_STORAGE_DRIVER environment variable that can be defined before tests run:

TEST_STORAGE_DRIVER=ASYNC_LOCAL_STORAGE npm run test

As I use newer version of npm, the package-lock.json got updated. There is one new dependency, semver. It could probably be removed if we decided on custom implementation, but I worried about the compatibility with older runtimes which may use unexpected version format.

Considerations:

• Once the PR is reviewed I suggest the default storageDriver option to be set to AUTO. For now it is set to CLS_HOOKED avoiding breaking change. By default package works as before, the new driver is opt-in.
• bindEmitter was removed; no tests indicated it's usefulness. Reading the implementation I haven't found any sensible scenario in which it would be required as part of this package. It is possible to recreate (not very hard) if needed, please provide test case.
• To make it easily testable some changes to internal data structures would be necessarily. Either the data should be bound to some user-controlled instance, or perhaps a reset() method could be provided - even if only for tests. Did not want to make too big of a change.

[Aliheym]

Hi, it looks cool. Let me check it on these weekends.

[ghost]

Happy to test and start using it, once merged!

[vsamofal]

@Aliheym @Aareksio love this feature,

is this lib abandoned, and it's better to host it on our own to get this feature?

[Aliheym]

Hi guys, sorry for such delay. It's been a busy period at work. I'll get it done today or tomorrow morning.

[Aliheym]

All tests have successfully passed. However, as rightly mentioned above, the current code does not allow for convenient testing of this feature without running it with different TEST_STORAGE_DRIVER env.

We need to modify the internal data structure, but this would be beyond the scope of the current PR. I believe we can roll out this feature and then I can focus on the necessary internal modifications.

Additionally, I also think we need to use AUTO as the default value

[Aareksio]

For tests, alternatively, you could run CI with different environments using matrix feature.

As for AUTO, I am not sure what is the best rollout strategy here - to release minor keeping cls hooked the default and change to AUTO with next major. Or release major right away.

[vsamofal]

Let me know if I can help with it

[Aliheym]

For tests, alternatively, you could run CI with different environments using matrix feature.

I will check, thanks.

As for AUTO, I am not sure what is the best rollout strategy here - to release minor keeping cls hooked the default and change to AUTO with next major. Or release major right away.

Hard question 🙃. Actually, I'm not thinking about a major version yet. In my opinion it would be better to release the minor version first with cls hooked the default as it is now. Next major, as you said, we can change to AUTO.

[Aliheym]

Thank you for your patience guys. I've merged this PR.