Add new endpoints to generate swh badges
Add endpoints /badge/(object_type)/(object_id)/
and /badge/(object_pid)/
to generate Github style like SVG badges for linking to the archive in
a README file.
Those new endpoints add CORS header to the HTTP responses in order to be used from a different domain than *.softwareheritage.org ones.
Below is a preview of the generated badges according to swh object type:
Colors and texts might still be improved.
Related to #2090 (closed)
Test Plan
Tests checking the badges are well-formed but also checking HTTP status codes when an error occurs have been added.
Migrated from D2310 (view on Phabricator)