0.5.1

Major changes:

• Update for compatibility with psycopg3
• Update to queryparser 0.7 for the full support of ADQL 2.1
• Improved stats module: added REST api and revisit the stored data

Small fixes and updates:

• Fixed several bugs in rendering of html and md
• Added list of the metadata for schemas at /metadata/
• Updated the management of the custom semantics for the DataLink