Add start time to request logger middleware values

[aldas]

Add start time to request logger middleware values to get time value just before next middleware/handler was called. Logger middlewares timestamps are for instants after handler next(c) has returned back to request logger scope. v.StartTime gives you time before.

See #1989 (comment)

[codecov]

Codecov Report

Merging #1991 (845ad5d) into master (4651c7a) will increase coverage by 0.00%.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##           master    #1991   +/-   ##
=======================================
  Coverage   91.23%   91.23%           
=======================================
  Files          33       33           
  Lines        2886     2887    +1     
=======================================
+ Hits         2633     2634    +1     
  Misses        161      161           
  Partials       92       92           

Impacted Files	Coverage Δ
middleware/request_logger.go	97.59% <100.00%> (+0.02%)	⬆️

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[aldas]

@pafuent please review

[pafuent]

LGTM!