The request body is truncated if it exceeds 8MB

[LGQ17]

Describe the bug
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To Reproduce
Steps to reproduce the behavior, if applicable:

1. The code is

rest\httpx\requests.go
reader := io.LimitReader(r.Body, maxBodyLen)

2. The error is

**Expected behavior**
A clear and concise description of what you expected to happen.

**Screenshots**
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**Environments (please complete the following information):**
- OS: [e.g. Linux]
- go-zero version [e.g. 1.2.1]
- goctl version [e.g. 1.2.1, optional]

**More description**
Add any other context about the problem here.

[LGQ17]

// ParseJsonBody parses the post request which contains json in body.
func ParseJsonBody(r *http.Request, v any) error {
if withJsonBody(r) {
reader := io.LimitReader(r.Body, maxBodyLen)
return mapping.UnmarshalJsonReader(reader, v)
}

return mapping.UnmarshalJsonMap(nil, v)

}

[kevwan]

There is MaxBytes in config, you can set the max body length.

[LGQ17]

maxBodyLen is a constant，use in httpx.Parse. setting MaxBytes does not solve the @kevwan

There is MaxBytes in config, you can set the max body length.