Conditional primitive supports params in path

[YuqiXiao]

Is your feature request related to a problem? Please describe.
Path route rule supported by BFE is req_path_in(/user), req_path_prefix_in(/user), req_path_suffix_in(user) which deals with path like /user, /user.* or .* user. But what if i want to add route rule like RESTFUL API path /teams/{teamId}/users/{userId}.

Describe the solution you'd like
Support a kind of conditional primitive to solve path like /teams/{teamId}/users/{userId} and extract params to request.

As route_rule: {req_params(/teams/{teamId}/users/{userId}), clusterName: "cluster"} , when facing with request's path: /teams/1/users/3 BFE could:

• match route rule and send the traffic to cluster;
• extract variables of the path and save the variables in request {"teamId": "1", "userId": "3"};

Describe alternatives you've considered
Here is the example: mux