add BeegoInput.RequestBody source to Beego framework

[gregxsunday]

The Controller.Context.BeegoInput.RequestBody source is not currently modelled. It seems like a go-to way to access a JSON request body using this framework.

Looks to me, like it's the only field in the class worth modelling:
https://pkg.go.dev/github.com/beego/beego/v2/server/web/context#BeegoInput

Here are examples of how this is used in practice:
https://cs.github.com/?q=Input.RequestBody%20language%3AGo&scopeName=All%20repos&scope=

I also wanted to add some tests showcasing this source but I must admit I'm quite overwhelmed as I'm new to CodeQL and most of the docs/guidelines are for people submitting new queries.

[smowton]

To add a test, add a function to https://github.com/github/codeql/blob/main/go/ql/test/library-tests/semmle/go/frameworks/Beego/test.go that would expose a problem via this field, e.g. by simulating an XSS vulnerability, then use codeql test run --learn go/ql/test/library-tests/semmle/go/frameworks/Beego to execute the test -- you should find the ReflectedXss.expected file is altered to reflect new results if the test worked as expected.

[gregxsunday]

Thanks @smowton, I added the test.
Unfortunately, I also added import of encoding/json which changed line numbers thus all of the .expected files changed as well. Perhaps we could force a test without adding the import but I've not encountered using the ctx.Input.RequestBody in a different context than json.Unmarshall.

[smowton]

Shame about the movement -- for that reason we've been shifting to Inline Expectation Tests, where we use a comment to indicate where results should occur and the .expected file records variances against the expectations (i.e., the good answer is the file is empty) -- however there's no need to go to that effort for just this change.

One last thing to change: the codeql-go repository is now merged into https://github.com/github/codeql -- please retarget your PR over there.

[gregxsunday]

I created another PR in that repo: github/codeql#10709
I hope that's what you meant by retarget, I didn't find a way to do this more elegantly. We can probably close this pr now.

[smowton]

Replaced by github/codeql#10709