Support encoded path in router

[life1347]

Encoded path means the URL path contains encoded string like "/foo%2Fbar".
Gorilla/Mux by default doesn't enable encoded path support, you need to enable
it when initializing the router.

This PR adds a new environment variable USE_ENCODED_PATH to router
deployment to enable encoded path support.

Fix #1317

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This change is 

[codecov]

Codecov Report

Merging #1347 into master will increase coverage by <.01%.
The diff coverage is 50%.

@@            Coverage Diff            @@
##           master   #1347      +/-   ##
=========================================
+ Coverage   27.39%   27.4%   +<.01%     
=========================================
  Files          70      70              
  Lines        7378    7383       +5     
=========================================
+ Hits         2021    2023       +2     
- Misses       5123    5124       +1     
- Partials      234     236       +2

Impacted Files	Coverage Δ
pkg/router/router.go	14.7% <50%> (+1.3%)	⬆️

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