JSON Request Keys Do Not Respect Variable Substitutions

[Enoz]

What is the current bug behavior?

JSON Keys in request object does not follow expected variable replacement logic
Related: #3592

Steps to reproduce

POST https://postman-echo.com/post
[Options]
variable: mykey="variable_value"
{
    "hardcoded_key": "hardcoded_value",
    "{{mykey}}": "some_other_value"
}

What is the expected correct behavior?

Expected
Request to submit as

{
    "hardcoded_key": "hardcoded_value",
    "variable_value": "some_other_value"
}

Current Behavior
Request is submitted as

{
    "hardcoded_key": "hardcoded_value",
    "{{mykey}}": "some_other_value"
}

Execution context

• Hurl Version (hurl --version):

hurl 6.0.0 (x86_64-pc-linux-gnu) libcurl/8.11.1 OpenSSL/3.4.0 zlib/1.3.1 brotli/brotli/1.1.0 zstd/zstd/1.5.6 libidn2/2.3.7 libssh2/1.11.1 nghttp2/1.64.0 quic/nghttp3/1.7.0
Features (libcurl):  alt-svc AsynchDNS brotli HSTS HTTP2 HTTP3 IDN IPv6 Largefile libz NTLM SPNEGO SSL TLS-SRP UnixSockets zstd
Features (built-in): brotli