Support localhost exception

[chilagrow]

Description

Closes #4100.

Readiness checklist

• I added/updated unit tests (and they pass).
• I added/updated integration/compatibility tests (and they pass).
• I added/updated comments and checked rendering.
• I made spot refactorings.
• I updated user documentation.
• I ran task all, and it passed.
• I ensured that PR title is good enough for the changelog.
• (for maintainers only) I set Reviewers (@FerretDB/core), Milestone (Next), Labels, Project and project's Sprint fields.
• I marked all done items in this checklist.

[codecov]

Codecov Report

Attention: Patch coverage is 73.68421% with 5 lines in your changes are missing coverage. Please review.

Project coverage is 73.83%. Comparing base (eb93ab1) to head (2c58bda).
Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #4156      +/-   ##
==========================================
+ Coverage   69.23%   73.83%   +4.60%     
==========================================
  Files         354      354              
  Lines       23013    23014       +1     
==========================================
+ Hits        15933    16993    +1060     
+ Misses       5723     4725     -998     
+ Partials     1357     1296      -61     

Files	Coverage Δ
ferretdb/ferretdb.go	86.51% <ø> (ø)
integration/setup/setup.go	81.37% <100.00%> (+0.12%)	⬆️
internal/clientconn/conninfo/conn_info.go	96.36% <100.00%> (-0.13%)	⬇️
internal/handler/commands.go	100.00% <100.00%> (ø)
internal/handler/msg_whatsmyuri.go	100.00% <100.00%> (ø)
internal/clientconn/conn.go	51.35% <33.33%> (+4.07%)	⬆️
internal/handler/authenticate.go	73.52% <50.00%> (+14.10%)	⬆️

... and 73 files with indirect coverage changes

Flag	Coverage Δ
filter-true	66.71% <73.68%> (+5.21%)	⬆️
hana-1	?
integration	66.71% <73.68%> (+5.21%)	⬆️
mongodb-1	4.84% <10.52%> (+0.03%)	⬆️
postgresql-1	46.17% <73.68%> (?)
postgresql-2	49.00% <68.42%> (-0.18%)	⬇️
postgresql-3	48.86% <57.89%> (+2.56%)	⬆️
sqlite-1	45.39% <73.68%> (?)
sqlite-2	48.19% <68.42%> (-0.16%)	⬇️
sqlite-3	48.03% <57.89%> (+2.66%)	⬆️
unit	32.93% <29.41%> (+0.01%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

[noisersup]

LGTM

[AlekSi]

@chilagrow Is it ready for re-review?

[chilagrow]

@chilagrow Is it ready for re-review?

Yes please!

[AlekSi]

Then re-request it :)

[rumyantseva]

LGTM!