feat: make it support rewrite request body in external plugins

[rubikplanet]

Description

make it support rewrite request body.

please update ext-plugin-proto first.

to make it be able to rewrite the request body in external plugins.

i don't have a full development environment for apisix. someone have the full development env can help to add the test code.

Fixes # (issue)

Checklist

• I have explained the need for this PR and the problem it solves
• I have explained the changes or the new features added to this PR
• I have added tests corresponding to this change
• I have updated the documentation to reflect this change
• I have verified that this change is backward compatible (If not, please discuss on the APISIX mailing list first)

[jiangfucheng]

This PR is based on api7/ext-plugin-proto#35, maybe we should wait for the PR to merge and then update the dependency version of ext-plugin-proto. And, we also need to add corresponding test.

[jiangfucheng]

Suggested change

	ngx.req.set_body_data(body)
	ngx.req.read_body()
	ngx.req.set_body_data(body)

We need call ngx.req.read_body() before set_body_data

[jiangfucheng]

https://github.com/apache/apisix/blob/59c1d99a6a571a77d9c3f7995a23785d93a4a92c/t/lib/ext-plugin.lua#L473C13-L473C13

Before this line, we can mock rewrite_request_body case:

        elseif case.rewrite_request_body == true then
            local len = 4
            http_req_call_rewrite.StartBodyVector(builder, len)
            builder:PrependByte(string.byte("\n"))
            builder:PrependByte(string.byte("c"))
            builder:PrependByte(string.byte("b"))
            builder:PrependByte(string.byte("a"))
            local b = builder:EndVector(len)

            http_req_call_rewrite.Start(builder)
            http_req_call_rewrite.AddBody(builder, b)
            local action = http_req_call_rewrite.End(builder)
            build_action(action, http_req_call_action.Rewrite)

And then, we can add test cases in plugin/ext-plugin/http-req-call.t

=== TEST 27: add route
--- config
    location /t {
        content_by_lua_block {
            local json = require("toolkit.json")
            local t = require("lib.test_admin")

            local code, message, res = t.test('/apisix/admin/routes/1',
                ngx.HTTP_PUT,
                 [[{
                    "uri": "/echo",
                    "plugins": {
                        "ext-plugin-pre-req": {
                        }
                    },
                    "upstream": {
                        "nodes": {
                            "127.0.0.1:1980": 1
                        },
                        "type": "roundrobin"
                    }
                }]]
            )

            if code >= 300 then
                ngx.status = code
                ngx.say(message)
                return
            end

            ngx.say(message)
        }
    }
--- response_body
passed



=== TEST 29: test rewrite request body
--- request
GET /echo
--- response_body chomp
cat
--- extra_stream_config
    server {
        listen unix:$TEST_NGINX_HTML_DIR/nginx.sock;

        content_by_lua_block {
            local ext = require("lib.ext-plugin")
            ext.go({rewrite_request_body = true})
        }
    }
--- response_body
abc

[jiangfucheng]

We aslo should update the documents.

[zxyao145]

Exciting feature, when can this PR be merged? Many people need this feature

1. bug: setBody not work apisix-java-plugin-runner#143
2. bug: request设置新的body替换客户端原请求body无效 apisix-java-plugin-runner#172
3. request help: rewrite request body apisix-java-plugin-runner#222
4. request help: How can i modify the request body with java plugin？ apisix-java-plugin-runner#252
5. request help: edit request body apisix-go-plugin-runner#127
6. how to use ext-plugin-pre-req change apisix request body。 base on apisix-go-plugin-runner apisix-go-plugin-runner#129