Set missing operation on AuthenticationForm

[FCsongradi]

Closes #793

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[mxr576]

LGTM :)

[codecov]

Codecov Report

Merging #792 (dfe5741) into 2.x (d235c18) will decrease coverage by 0.04%.
The diff coverage is 0.00%.

@@             Coverage Diff              @@
##                2.x     #792      +/-   ##
============================================
- Coverage     44.86%   44.83%   -0.04%     
- Complexity     2899     2900       +1     
============================================
  Files           337      337              
  Lines         10718    10727       +9     
============================================
  Hits           4809     4809              
- Misses         5909     5918       +9     

Impacted Files	Coverage Δ
src/Form/AppApiKeyAddFormBase.php	0.00% <0.00%> (ø)
src/Form/AuthenticationForm.php	0.00% <ø> (ø)

[shishir-intelli]

Thanks for your contribution @FCsongradi and @mxr576 !
LGTM too