Host isolation

[arcusfelis]

it's a variant of #3064 but to master.

Proposed changes include:

• there is no code or solution for multi-tenancy.
• the code would probably change, once we add dynamic domains.
• could be merged to master, but multi-tenancy would have to be rebased on master to continue work on this feature. Routing would also have to be working.

[codecov]

Codecov Report

Merging #3070 (5131e73) into master (8a4e707) will decrease coverage by 0.00%.
The diff coverage is 96.29%.

@@            Coverage Diff             @@
##           master    #3070      +/-   ##
==========================================
- Coverage   78.76%   78.76%   -0.01%     
==========================================
  Files         378      379       +1     
  Lines       31102    31129      +27     
==========================================
+ Hits        24499    24518      +19     
- Misses       6603     6611       +8     

Impacted Files	Coverage Δ
src/config/mongoose_config_spec.erl	98.80% <ø> (ø)
src/mod_domain_isolation.erl	96.29% <96.29%> (ø)
src/ejabberd.erl	45.00% <0.00%> (-10.00%)	⬇️
...bal_distrib/mod_global_distrib_hosts_refresher.erl	71.69% <0.00%> (-1.89%)	⬇️
src/wpool/mongoose_wpool.erl	81.00% <0.00%> (-1.00%)	⬇️
src/global_distrib/mod_global_distrib_utils.erl	65.09% <0.00%> (-0.95%)	⬇️
src/ejabberd_sm.erl	75.91% <0.00%> (-0.61%)	⬇️
src/mod_bosh_socket.erl	78.88% <0.00%> (-0.32%)	⬇️
src/mod_muc_room.erl	77.50% <0.00%> (-0.06%)	⬇️
src/mod_muc_log.erl	77.72% <0.00%> (ø)
... and 3 more

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 8a4e707...5131e73. Read the comment docs.

[NelsonVides]

LGTM