Use displayname as file name when downloading a contact

[skjnldsv]

fix #1019

[codecov]

Codecov Report

Merging #1022 into master will not change coverage.
The diff coverage is n/a.

@@          Coverage Diff           @@
##           master   #1022   +/-   ##
======================================
  Coverage      60%     60%           
======================================
  Files           4       4           
  Lines          60      60           
======================================
  Hits           36      36           
  Misses         24      24

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