Refactored hook handlers in mod_register

[pawlooss1]

This PR changes all hook handlers in mod_register module to gen_hook format.

[codecov]

Codecov Report

Base: 82.77% // Head: 83.13% // Increases project coverage by +0.36% 🎉

Coverage data is based on head (60e2a05) compared to base (0b93aa8).
Patch coverage: 90.90% of modified lines in pull request are covered.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #3867      +/-   ##
==========================================
+ Coverage   82.77%   83.13%   +0.36%     
==========================================
  Files         535      535              
  Lines       34149    34153       +4     
==========================================
+ Hits        28266    28393     +127     
+ Misses       5883     5760     -123     

Impacted Files	Coverage Δ
src/mod_register.erl	75.00% <85.71%> (+0.12%)	⬆️
src/mongoose_hooks.erl	95.89% <100.00%> (+0.02%)	⬆️
src/mongoose_cleaner.erl	60.00% <0.00%> (-10.00%)	⬇️
src/muc_light/mod_muc_light_db_mnesia.erl	91.57% <0.00%> (-1.06%)	⬇️
src/mod_muc_log.erl	62.82% <0.00%> (ø)
src/pubsub/mod_pubsub.erl	73.23% <0.00%> (+0.18%)	⬆️
src/pubsub/mod_pubsub_db_rdbms.erl	95.34% <0.00%> (+0.25%)	⬆️
src/rdbms/mongoose_rdbms.erl	66.31% <0.00%> (+1.05%)	⬆️
src/metrics/mongoose_metrics.erl	92.47% <0.00%> (+1.07%)	⬆️
src/inbox/mod_inbox_rdbms_async.erl	73.52% <0.00%> (+1.47%)	⬆️
... and 8 more

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[mongoose-im]

small_tests_24 / small_tests / 60e2a05
Reports root / small

---

small_tests_25 / small_tests / 60e2a05
Reports root / small

---

dynamic_domains_pgsql_mnesia_24 / pgsql_mnesia / 60e2a05
Reports root/ big
OK: 4084 / Failed: 0 / User-skipped: 88 / Auto-skipped: 0

---

ldap_mnesia_24 / ldap_mnesia / 60e2a05
Reports root/ big
OK: 2149 / Failed: 0 / User-skipped: 804 / Auto-skipped: 0

---

ldap_mnesia_25 / ldap_mnesia / 60e2a05
Reports root/ big
OK: 2149 / Failed: 0 / User-skipped: 804 / Auto-skipped: 0

---

dynamic_domains_mysql_redis_25 / mysql_redis / 60e2a05
Reports root/ big
OK: 4058 / Failed: 0 / User-skipped: 114 / Auto-skipped: 0

---

dynamic_domains_pgsql_mnesia_25 / pgsql_mnesia / 60e2a05
Reports root/ big
OK: 4084 / Failed: 0 / User-skipped: 88 / Auto-skipped: 0

---

dynamic_domains_mssql_mnesia_25 / odbc_mssql_mnesia / 60e2a05
Reports root/ big
OK: 4084 / Failed: 0 / User-skipped: 88 / Auto-skipped: 0

---

elasticsearch_and_cassandra_25 / elasticsearch_and_cassandra_mnesia / 60e2a05
Reports root/ big
OK: 2637 / Failed: 0 / User-skipped: 655 / Auto-skipped: 0

---

internal_mnesia_25 / internal_mnesia / 60e2a05
Reports root/ big
OK: 2291 / Failed: 0 / User-skipped: 662 / Auto-skipped: 0

---

pgsql_mnesia_24 / pgsql_mnesia / 60e2a05
Reports root/ big
OK: 4458 / Failed: 0 / User-skipped: 97 / Auto-skipped: 0

---

riak_mnesia_24 / riak_mnesia / 60e2a05
Reports root/ big
OK: 2481 / Failed: 0 / User-skipped: 641 / Auto-skipped: 0

---

pgsql_mnesia_25 / pgsql_mnesia / 60e2a05
Reports root/ big
OK: 4458 / Failed: 0 / User-skipped: 97 / Auto-skipped: 0

---

mysql_redis_25 / mysql_redis / 60e2a05
Reports root/ big
OK: 4444 / Failed: 0 / User-skipped: 111 / Auto-skipped: 0

---

mssql_mnesia_25 / odbc_mssql_mnesia / 60e2a05
Reports root/ big
OK: 4458 / Failed: 0 / User-skipped: 97 / Auto-skipped: 0

[NelsonVides]

LGTM 👌🏽