enable autopkgtests for diaspora

The following dependencies are required to enable autopkgtest

• fixture_builder (= 0.5.2) @avron
• rspec-json_expectations 2.1 @avron
• json-schema-rsepc 0.0.4
• cucumber-api-steps 0.14 @avron

Reintroduce to archive

• phantomjs - https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=962061 (package was orphaned and depended on python 2)

Update dependency

• ruby-database-cleaner 1.8.3 @sahilister

Update dependency in buster-backports

• ruby-fuubar 2.5.0

This list is incomplete...

Work in progress code in autopkgtest branch https://salsa.debian.org/ruby-team/diaspora/-/commits/autopkgtest/