AppendPath parameter

[samutamm]

As consequence of #472, it's now possible to have following custom-data:

rebuild: true
list:
 - key: bob-bananas
   username: bob
   extra-field: ...

 - key: bob-pearls
   username: bob
   extra-field: ...

and following configuration for HeaderLookup:

name: headerLookup
kind: HeaderLookup
headerKey: "X-AUTH-USER"
etcdPrefix: "credentials/"
headerSetters:
  - etcdKey: "extra-field"
    headerKey: "user-extra-field"

that aims to retrieve the extra-field of the authenticated user. However if the authenticated user is bob (= value of X-AUTH-USER header is bob), bob cannot retrieve data entries bob-bananas and bob-pearls.

This PR aims to solve this by introducing pathRegExp parameter that extracts specified part of the path and appends it to the custom-data key, when retrieving data. Let's change the configuration of the HeaderLookup to

name: headerLookup
kind: HeaderLookup
headerKey: "X-AUTH-USER"
etcdPrefix: "credentials/"
pathRegExp: "^/(.+)" # add this line
headerSetters:
  - etcdKey: "extra-field"
    headerKey: "user-extra-field"

Now when header("X-AUTH-USER") = "bob" and request path = /bananas, the HeaderLookup retrieves the custom-data entry bob-bananas.

[codecov-commenter]

Codecov Report

Merging #476 (04316af) into main (3c21251) will increase coverage by 0.03%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##             main     #476      +/-   ##
==========================================
+ Coverage   80.29%   80.33%   +0.03%     
==========================================
  Files          83       83              
  Lines        9676     9685       +9     
==========================================
+ Hits         7769     7780      +11     
+ Misses       1464     1463       -1     
+ Partials      443      442       -1     

Impacted Files	Coverage Δ
pkg/filter/headerlookup/headerlookup.go	88.81% <100.00%> (+5.22%)	⬆️
pkg/filter/validator/basicauth.go	78.89% <0.00%> (-1.84%)	⬇️

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