Add support for OpenPGP keys attached to email resources

See merge request !46

Add an API endpoint to set/unset OpenPGP keys attached to email resources.

This is auxiliary data, so it's best to time out early if the backends
are unreachable and still have time to return the User response.

Support Webauthn

See merge request !42

Add tests for that too.

Add enable/disable OTP tests, and a delete ASP test.

The API change is semantically backwards-incompatible, i.e. it will
default to no change unless you set the new set_foo attributes.

Resolves potential conflict when tests are run in parallel.

The composite types can be serialized to JSON without issues or
needing any additional precautions, and the resulting code is
simpler.

Update golang.org/x/net commit hash to 60bc85c

See merge request !29

Fix some issues reported by lintian

See merge request !36

Update golang.org/x/crypto commit hash to 32db794

See merge request !32

Update module github.com/go-ldap/ldap/v3 to v3.4.1

See merge request !37

Changes-By: lintian-brush
Fixes: lintian: package-uses-old-debhelper-compat-version
See-also: https://lintian.debian.org/tags/package-uses-old-debhelper-compat-version.html

Fix some issues reported by lintian

See merge request !35

Changes-By: lintian-brush
Fixes: lintian: missing-built-using-field-for-golang-package
See-also: https://lintian.debian.org/tags/missing-built-using-field-for-golang-package.html

Changes-By: lintian-brush
Fixes: lintian: uses-debhelper-compat-file
See-also: https://lintian.debian.org/tags/uses-debhelper-compat-file.html

+ Use dh_installsystemd rather than deprecated dh_systemd_enable.
+ Use dh_installsystemd rather than deprecated dh_systemd_start.

Changes-By: lintian-brush
Fixes: lintian: package-uses-old-debhelper-compat-version
See-also: https://lintian.debian.org/tags/package-uses-old-debhelper-compat-version.html

Changes-By: lintian-brush
Fixes: lintian: missing-build-dependency-for-dh-addon
See-also: https://lintian.debian.org/tags/missing-build-dependency-for-dh-addon.html

Changes-By: lintian-brush
Fixes: lintian: trailing-whitespace
See-also: https://lintian.debian.org/tags/trailing-whitespace.html

Update module github.com/prometheus/client_golang to v1.11.0

See merge request !34