Add dynamic timestamp to request payload

[danny-dainton]

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Dynamic variable timestamp in milliseconds

Once a variable has been created and stored, it can be referenced in the body like this: { "time": "{{timestampMs}}" }

Adding it to an existing string value would just be like this:

{
    "idRichiesta": "0001234_00004555_{{timestampMs}}",
    "timestamp": "{{timestampMs}}"
}