Put mod_disco opts in a map with defaults

[chrzaszcz]

Also:

• Order default_mod_config alphabetically.
• Add mod_config/2 helper
• Minor fix in the docs
• Removed the special case of undefined module treated as mod_disco - it was counter-intuitive.

[codecov]

Codecov Report

Merging #3550 (c6cb0f0) into master (a89e2ec) will decrease coverage by 0.06%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master    #3550      +/-   ##
==========================================
- Coverage   79.26%   79.20%   -0.07%     
==========================================
  Files         420      420              
  Lines       32266    32263       -3     
==========================================
- Hits        25577    25555      -22     
- Misses       6689     6708      +19     

Impacted Files	Coverage Δ
src/mongoose_disco.erl	94.82% <ø> (ø)
src/mod_caps.erl	75.57% <100.00%> (ø)
src/mod_disco.erl	87.61% <100.00%> (+0.58%)	⬆️
src/event_pusher/mod_event_pusher.erl	65.00% <0.00%> (-22.50%)	⬇️
...bal_distrib/mod_global_distrib_hosts_refresher.erl	71.69% <0.00%> (-1.89%)	⬇️
src/rdbms/mongoose_rdbms.erl	62.17% <0.00%> (-1.13%)	⬇️
src/mam/mod_mam_rdbms_arch_async.erl	96.62% <0.00%> (-1.13%)	⬇️
src/pubsub/mod_pubsub.erl	73.19% <0.00%> (-0.42%)	⬇️
src/ejabberd_sm.erl	84.59% <0.00%> (-0.33%)	⬇️
src/global_distrib/mod_global_distrib_receiver.erl	81.11% <0.00%> (+2.22%)	⬆️

---

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 a89e2ec...c6cb0f0. Read the comment docs.

[mongoose-im]

small_tests_23 / small_tests / c6cb0f0
Reports root / small

---

small_tests_24 / small_tests / c6cb0f0
Reports root / small

---

dynamic_domains_mysql_redis_24 / mysql_redis / c6cb0f0
Reports root/ big
OK: 2704 / Failed: 0 / User-skipped: 256 / Auto-skipped: 0

---

dynamic_domains_pgsql_mnesia_23 / pgsql_mnesia / c6cb0f0
Reports root/ big
OK: 2721 / Failed: 0 / User-skipped: 239 / Auto-skipped: 0

---

dynamic_domains_mssql_mnesia_24 / odbc_mssql_mnesia / c6cb0f0
Reports root/ big
OK: 2721 / Failed: 0 / User-skipped: 239 / Auto-skipped: 0

---

dynamic_domains_pgsql_mnesia_24 / pgsql_mnesia / c6cb0f0
Reports root/ big
OK: 2721 / Failed: 0 / User-skipped: 239 / Auto-skipped: 0

---

internal_mnesia_24 / internal_mnesia / c6cb0f0
Reports root/ big
OK: 1551 / Failed: 0 / User-skipped: 349 / Auto-skipped: 0

---

elasticsearch_and_cassandra_24 / elasticsearch_and_cassandra_mnesia / c6cb0f0
Reports root/ big
OK: 1685 / Failed: 0 / User-skipped: 369 / Auto-skipped: 0

---

ldap_mnesia_24 / ldap_mnesia / c6cb0f0
Reports root/ big
OK: 1510 / Failed: 0 / User-skipped: 390 / Auto-skipped: 0

---

mysql_redis_24 / mysql_redis / c6cb0f0
Reports root/ big
OK: 3090 / Failed: 0 / User-skipped: 253 / Auto-skipped: 0

---

pgsql_mnesia_23 / pgsql_mnesia / c6cb0f0
Reports root/ big
OK: 3095 / Failed: 0 / User-skipped: 248 / Auto-skipped: 0

---

pgsql_mnesia_24 / pgsql_mnesia / c6cb0f0
Reports root/ big
OK: 3095 / Failed: 0 / User-skipped: 248 / Auto-skipped: 0

---

mssql_mnesia_24 / odbc_mssql_mnesia / c6cb0f0
Reports root/ big
OK: 3095 / Failed: 0 / User-skipped: 248 / Auto-skipped: 0

---

riak_mnesia_24 / riak_mnesia / c6cb0f0
Reports root/ big
OK: 1690 / Failed: 0 / User-skipped: 364 / Auto-skipped: 0

[gustawlippa]

Looks good 👍