Add MFA level validation

[jenshenny]

No description provided.

[codecov]

Codecov Report

Merging #3870 (7633d1b) into master (f2e6b46) will decrease coverage by 0.32%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master    #3870      +/-   ##
==========================================
- Coverage   98.79%   98.47%   -0.32%     
==========================================
  Files         215      215              
  Lines        5372     5375       +3     
==========================================
- Hits         5307     5293      -14     
- Misses         65       82      +17     

Impacted Files	Coverage Δ
app/models/concerns/user_multifactor_methods.rb	100.00% <100.00%> (ø)

... and 2 files with indirect coverage changes

[bettymakes]

Since @ericherscovich took this issue over, let's close this in favour of shipping this PR.

[simi]

Since @ericherscovich took this issue over, let's close this in favour of shipping this PR.

closing