JSON Extractors do not allow variables in queries

[5731la]

When processing a JSON extractor, compiling occurs prior to runtime (compile.go#L33), and as such, templated variables are not processed.

Template example:

id: catapi
info:
  name: catapi test template
  author: Stella
  severity: critical
  description: test template call that should always return as critical
  tags: meow,meowmeow,meowmeowmeow
variables:
  catid: '[a-zA-Z0-9]'
http:
  - id: bulk-sisid-takeover
    method: GET
    path:
      - "https://api.thecatapi.com/v1/images/search?limit=10"
    extractors:
      - type: json
        part: body
        name: id
        # Find a URL based on a catid specified in a variable or extractor, if it exists, extract it. 
        json:
          - '(.[] | select(.id | test("{{catid}}")) | .url)'

Expected behavior:

This always returns a finding as this regular expression is checking if the URL contains any letters/numbers.

Actual behavior:

Never returns, as it is testing for {{catid}} literally rather than filling the variable.

Proposed fixes:

1. Clearly document that this is a limitation of this (and ALL) extractors (this limitation also applies to extractors, built-in variables like {{BaseURL}}, etc)
2. Perform Just-In-Time compilation of extractors with the variables substituted in
3. Use gojq's WithVariables