request help: Need to rewrite the http request method

[SherrillJoyceGit]

Issue description

I need to rewrite the http request method.
I think about two ways, but both failed.
Way 1.
Add a method like "(r *Request) SetPath". As a result , I add a method to Request and call hrc.Req. MutateMethod.
It only changes the object of Request.r and does not change the buffer object(generated by flatbuffer which is a rpc solution of google). The program just use the content of buffer object to call the upstream api.

Way 2.
Based on way1 , there is no function at HTTPReqCall.Rewrite to change the method. I try to use functions of HTTPReqCall.Req to rebuild the buffer. It does't work and lua problems occurred ！

Why:

We have some apis using the Get methods, and the client only use POST methods that can't be changed.
Client -> Method(POST) -> configuration in plugins -> Go Runner Plugin -> Method(GET) -> Upstream

screenshots:

Environment

• APISIX Go Plugin Runner's version: v0.5.0
• APISIX version: v3.6.0
• Go version: 1.19.5
• OS (cmd: uname -a): Linux localhost.localdomain 3.10.0-862.el7.x86_64 ci: enable #1 SMP Fri Apr 20 16:44:24 UTC 2018 x86_64 x86_64 x86_64 GNU/Linux

[SherrillJoyceGit]

Finally，I do the request method change by writing a lua plugin.

[thinkdb1]

我最近实验修改重写body时，获得一点思路，虽然没有实验希望可以帮到你：
在apisix-core-with-plugin/internal/http/request.go中的(r *Request) FetchChanges(id uint32, builder *flatbuffers.Builder)的方法里面的hrc.RewriteStart(builder)下面，添加hrc.ReqAddMethod()这个方法，是不是可以实现重写method的方法，因为我加入hrc.RewriteAddBody这个方法后，可以重写body。当然前面要自己定义相关判断是否修改method

[TomCN0803]

I've started a pull request: #151
Features and modifications includes:

• Update github.com/api7/ext-plugin-proto to v0.6.1
• Add SetBody([]byte) to http.Request
• Add a sample request body rewrite plugin
• Add an e2e test for the sample request body rewrite plugin
• Lint some code and add items (e.g. .vscode, go.work) to .gitignore