Document request variables in .http files

[tdykstra]

Fixes #34607
Fixes #33729
Fixes #32668

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aspnetcore/test/http-files.md	Use .http files in Visual Studio 2022

[Copilot]

Copilot reviewed 1 out of 1 changed files in this pull request and generated 3 comments.

Comments suppressed due to low confidence (3)

aspnetcore/test/http-files.md:226

• The JSONPath expression should use '$.token' instead of 'token'.

{{login.response.body.$.token}}

aspnetcore/test/http-files.md:230

• The XPath expression should use '/token' instead of './token'.

{{login.response.body./token}}

aspnetcore/test/http-files.md:243

• There is a missing space after '#@name'. It should be '# @name login'.

#@name login

[Copilot]

There is a missing comma after '"username": "{{myusername}}"'.

Suggested change

	"username": "{{myusername}}",
	"username": "{{myusername}}"

[sayedihashimi]

Sorry for the delay, I reviewed the changes and they look good. Thanks a lot for putting this together. I'm working on a post for the VS blog as well. I'll link to the doc.