Release version 0.15.6
Merge Release 0.15.6
[enhancement] add workaround for empty date
[release] updated version for maintenance
[fix] change registration activate from put to patch
Release version 0.15.7
Merge Release 0.15.7
Release version 0.16
Merge Release 0.16
Release version 0.17
Merge Release 0.17
Release version 0.17.1
Merge Release 0.17.1
Update RELEASE.NOTES
Release version 0.18
Merge Release 0.18
Merge remote-tracking branch 'upstream/master' into develop

Conflicts:
	auth-server/pom.xml
	interaction-model/pom.xml
	pom.xml
	registration-module/pom.xml
	resource-server/pom.xml
Release version 0.20
Merge Release 0.20
Release version 0.21