Documenting webhooks

[ddorian]

This is a draft to ask for opinion. @lafrech

[codecov[bot]]

Codecov Report

Patch coverage: 37.50% and project coverage change: -0.56% :warning:

Comparison is base (d57a6fb) 99.88% compared to head (bfdff3d) 99.32%. Report is 1 commits behind head on master.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #553 +/- ## ========================================== - Coverage 99.88% 99.32% -0.56% ========================================== Files 14 14 Lines 885 892 +7 Branches 192 192 ========================================== + Hits 884 886 +2 - Misses 0 5 +5 Partials 1 1 ``` | [Files Changed](https://app.codecov.io/gh/marshmallow-code/flask-smorest/pull/553?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=marshmallow-code) | Coverage Δ | | |---|---|---| | [flask\_smorest/\_\_init\_\_.py](https://app.codecov.io/gh/marshmallow-code/flask-smorest/pull/553?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=marshmallow-code#diff-Zmxhc2tfc21vcmVzdC9fX2luaXRfXy5weQ==) | `87.80% <37.50%> (-12.20%)` | :arrow_down: |

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[ddorian]

@lafrech

What about an api like:

class SchemaClass(marshmallow.Schema):
    """Doc used as request description"""
    pass

class Blueprint2(flask_smorest.Blueprint):
    def register_webhook(SchemaClass, optional[tags, description, response, etc]):
        self.webhooks.append(webhook)

class Api2(flask_smorest.Api):
    def register_blueprint():
        super()
        # register webhooks
        for webhook in blp.webhooks:
             self.add_webhook_to_doc(class, tags, etc)

[lafrech]

Thanks for contributing and sorry about the delay.

I don't use webhooks myself and I don't when I'll have the time to look into this seriously.

Let's keep this open and anyone interested in the feature is welcome to join.