Extend test suite to cover functionality that we test manually now

[tripu]

• File type detection, eg Update file-type to version 3.9.0 🚀 #366
• Time and date manipulations, eg Update moment to version 2.15.2 🚀 #368
• Handling of attached (TAR) files, eg Update multer to version 1.2.1 🚀 #387
• LDAP lookup, eg Update ldapauth-fork to version 3.0.0 🚀 #388 (rely on a public LDAP server for tests?)

See also #247.

[tripu]

Also:

• Test automatically new CR workflow with GH issues
  (Extend the test suite; cf https://github.com/w3c/echidn/pull/575 )