feat(store): improve action decorator types

[ConnorUllmann]

PR Checklist

Please check if your PR fulfills the following requirements:

• [X] The commit message follows our guidelines: https://github.com/ngxs/store/blob/master/CONTRIBUTING.md#commit
• [X] Tests for the changes have been added (for bug fixes / features)
• [ ] Docs have been added / updated (for bug fixes / features)

PR Type

What kind of change does this PR introduce?

[ ] Bugfix
[X] Feature
[ ] Code style update (formatting, local variables)
[ ] Refactoring (no functional changes, no api changes)
[ ] Build related changes
[ ] CI related changes
[ ] Documentation content changes
[ ] Other... Please describe:

What is the current behavior?

The @Action decorator does not enforce that the actions passed to the decorator match the payloads expected by the method it decorates.

A simple example is the following—the below action has a payload { value: string } but the handler expects { value: number } incorrectly. This does not produce an error.

class ActionString {
  static type = 'action1';
  constructor(public value: string) {}
}

...

@Action(ActionString)
handler(context: StateContext<any>, payload: { value: number }) {}

Issue Number: N/A

What is the new behavior?

In the above example, a type error occurs. The case of multiple actions is also handled, requiring that a union of the payloads is accepted by the method.

Does this PR introduce a breaking change?

[ ] Yes
[X] No

This change is likely to introduce type errors, but it is not intended to impact runtime behavior.

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[bundlemon[bot]]

BundleMon (Integration Projects)

Unchanged files (2)

Status | Path | Size | Limits :------------: | ------------ | :------------: | :------------: :white_check_mark: | Main bundles(Gzip)
_{hello-world-ng17/dist-integration/main.(hash)
.js}
| 68.5KB | +1% :white_check_mark: | Main bundles(Gzip)
_{hello-world-ng16/dist-integration/main.(hash)
.js}
| 67.03KB | +1%

Total files change -3B 0%

Final result: :white_check_mark:

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Current branch size history | Target branch size history

[codeclimate[bot]]

Code Climate has analyzed commit a9f4ff32 and detected 0 issues on this pull request.

The test coverage on the diff in this pull request is 100.0% (50% is the threshold).

This pull request will bring the total coverage in the repository to 95.3% (0.0% change).

View more on Code Climate.