Data List: Extends ContentmentContentContext to access parentId Form and JSON data

[leekelleher]

Description

Transpires that the client-side patch I submitted for the BlockList editor (in umbraco/Umbraco-CMS#15063), didn't work. This is due to how ContentmentContentContext was trying to access the id and parentId parameters (on the querystring URL). However, the BlockList editor makes a POST request to the GetEmptyByKeys() endpoint, but not only that, the parentId is within a JSON blob sent in the body of the POST request. Which sounds fine, read the JSON from the request body and all good.

Not so fast! Turns out that in ASP.NET Core, the Request.Body can only be read once, which in the case of the GetEmptyByKeys() endpoint, that's done with the model-binding (of the ContentTypesByKeys type).

So to access the request body contents multiple times, you need to enable request.EnableBuffering(). From searching through Umbraco source, I found that there is an extension method called GetRawBodyStringAsync(), which even has the .EnableBuffering() call in it, super, job done.

Not so fast! Turns out that request.EnableBuffering() must be done at app-startup. Now, I needed a way to add a middleware to configure the request buffering, but I didn't want to enable this for all request (as it's considered a small performance hit), so I wanted to have a conditional middleware for a specific route/path.

I found this blog post super helpful in figuring out how to do this:
https://markb.uk/asp-net-core-read-raw-request-body-as-string.html

TL,DR; Contentment adds a conditional middleware to the GetEmptyByKeys() API route to enable buffering of the request body contents, so that it can be accessed again during the request lifecycle.

Please note, that I have targeted this PR on (upcoming) Contentment v5, as it (currently) only relevant for the BlockList editor patch available in Umbraco v13.1.0. I do not intend to backport it to Contentment v4.6.x, that is, unless there is a good enough reason to do so.

Related Issues?

• Data List: Extend ContentmentContentContext to access parentId form data (POST requests) #388

Types of changes

• Documentation change
• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist

• My code follows the coding style of this project.
• My changes generate no new warnings.
• My change requires a change to the documentation.
• I have updated the corresponding documentation.
• I have read the CONTRIBUTING and CODE_OF_CONDUCT documents.