Proxy: Fix nil pointer panic in BuildStreamURL and resource leak in ParseBody

[sevico]

Problem

Two bugs in internal/utils/utils.go:

1. Nil pointer panic in BuildStreamURL

net.ParseIP() returns nil for non-IP hostnames (e.g., "example.com"). The code calls ip.To4() without checking if ip is nil first, which causes a panic crash.

// Before: panics when hostname is not an IP address
if ip := net.ParseIP(u.Hostname()); ip.To4() != nil {

// After: safe nil check
if ip := net.ParseIP(u.Hostname()); ip != nil && ip.To4() != nil {

2. Resource leak in ParseBody

defer r.Close() is placed after the ReadAll error check. If ReadAll fails, the function returns early without the defer being registered, so r is never closed.

// Before: r.Close() not reached on ReadAll error
func ParseBody(r io.ReadCloser, v interface{}) error {
    b, err := ioutil.ReadAll(r)
    if err != nil {
        return errors.Wrapf(err, "read body") // r is never closed
    }
    defer r.Close()

// After: r always closed
func ParseBody(r io.ReadCloser, v interface{}) error {
    defer r.Close()
    b, err := ioutil.ReadAll(r)

Impact

• BuildStreamURL panics when the stream URL contains a domain name instead of an IP address.
• ParseBody leaks HTTP request body on read errors.

[suzp1984]

I rebased your branch to develop branch.
And this commit make sense.

[suzp1984]

One more thing, I added UT to cover this PR.