implement 'urlQueryEscape' and 'urlQueryUnescape' template functions in builtin extraFuncs

[KevinQiangK]

This commit adds the 'urlQueryEscape' and 'urlQueryUnescape' functions to the template's extra functions ('extraFuncs'). These functions provide URL encoding and decoding capabilities.

[codecov-commenter]

Codecov Report

Attention: 2 lines in your changes are missing coverage. Please review.

Comparison is base (a2c3f72) 79.65% compared to head (ab8d60f) 79.66%.
Report is 1 commits behind head on main.

Files	Patch %	Lines
pkg/filters/builder/extrafuncs.go	75.00%	1 Missing and 1 partial ⚠️

❗ Your organization needs to install the Codecov GitHub app to enable full functionality.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1194      +/-   ##
==========================================
+ Coverage   79.65%   79.66%   +0.01%     
==========================================
  Files         153      153              
  Lines       17402    17410       +8     
==========================================
+ Hits        13861    13870       +9     
+ Misses       2866     2865       -1     
  Partials      675      675              

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

[suchen-sci]

Hi, what's the difference between urlQueryEscape and urlquery?
And could you please tell me why we need to add urlQueryEscape if there are already urlquery?

[KevinQiangK]

urlquery is a built-in template function in the Go template package, and it has the same implementation as urlQueryEscape. The reason for adding both urlQueryEscape and urlQueryUnescape functions simultaneously serves two purposes:

1. To provide a clearer expression of functionality, as these functions are implemented using the queryEscape and queryUnescape methods from the url package.
2. To maintain consistency within Easegress by using symmetric function names.