Add configuration and code to opt-in to reduced logging.

[henryk]

Currently this strips all the boilerplate prefix and suffix from the packet dump in FinTSHTTPSConnection.send(), only showing the net payload.

[codecov[bot]]

Codecov Report

Merging #117 into master will decrease coverage by 0.17%. The diff coverage is 71.87%.

@@            Coverage Diff             @@
##           master     #117      +/-   ##
==========================================
- Coverage   87.48%   87.30%   -0.18%     
==========================================
  Files          23       23              
  Lines        3117     3144      +27     
==========================================
+ Hits         2727     2745      +18     
- Misses        390      399       +9     

Impacted Files	Coverage Δ
fints/utils.py	62.17% <68.75%> (+0.49%)	:arrow_up:
fints/connection.py	86.48% <75.00%> (-9.67%)	:arrow_down:

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