Tyk header variable substitution is not possible for certain JWT claims

[LowCostCustoms]

Branch/Environment/Version

• Branch/Version: Master
• Environment: On-prem

Describe the bug

When context variables are enabled and JWT/OAuth client authentication is configured, Tyk sets jwt_claims_{claim name} context variables to the corresponding JWT claim values. However, no variable name pre-processing is done, and the actual dictionary of context variables could contain records such as jwt_claims_https://my-api/my-claim. Due to the Tyk variable substitution limits, it's impossible to reference such properties from request/response header expressions.

Reproduction steps

1. Spin up a Tyk service using a configuration that is similar to the attached one.
2. Make a request using a valid JWT, for instance curl http://localhost:8080/ -H"Authorization: Bearer $token"

Actual behavior

$.headers.X-Forwarded-User-Id response property is set to ://my-domain.org/email value.

Expected behavior

A user can configure passing a claim from a client request JWT to a request header.

Configuration (tyk config file):

{
  "name": "my-api",
  "api_id": "my-api",
  "org_id": "my-org",
  "proxy": {
    "listen_path": "/",
    "target_url": "https://httpbin.org/headers",
    "preserve_host_header": false
  },
  "version_data": {
    "not_versioned": true,
    "versions": {
      "Default": {
        "name": "Default",
        "global_headers": {
          "X-Forwarded-User-Id": "$tyk_context.jwt_claims_https://my-domain.org/email"
        }
      }
    }
  },
  "use_openid": true,
  "openid_options": {
    "providers": [
      {
        "issuer": "https://my-domain.auth0.com/",
        "client_ids": {
          "aHR0cHM6Ly9teS1hcGkubXktb3JnLmNvbQ==": "undefined"
        }
      }
    ]
  },
  "jwt_scope_to_policy_mapping": {
    "my-scope": "everything"
  },
  "enable_context_vars": true
}

Additional context