[FEATURE] Show Server Variables in INSERT templates and SHOW METHODS

Feature Description
If a server variable is defined in the API spec, this variable should be shown in INSERT templates by default, for example, given the servers object in a Okta API spec...

servers:
- url: https://{subdomain}.okta.com/
  variables:
    subdomain:
      default: my-domain

Then SHOW INSERT INTO okta.identityprovider.idps should return...

INSERT INTO okta.identityprovider.idps(
  data__name,
  ...
  data__subdomain
)
SELECT
  '{{ .values.data__name }}',
   ...
  '{{ .values.data__subdomain }}';

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