Delete submissions, code updates and updated submission schema

[2.7]

Added

• Delete submission endpoint, with json example (under demo files) and test

Changed

• Updated API submission schema to the latest available on ncbi/clinvar GitHub pages
• Modified the json submission example to use one from the ClinVar GitHib repo (sample_clinical_significance_hgvs_submission.json)
• Removed the example of an old json submission (before 2022-11-21)
• Updated actions using the latest base images and to run using Python 3.9
• Docker image uses Python 3.11 instead of 3.8
• Replaced deprecated app "on event" with app lifespan

Fixed

• Updated issue templates
• Updated a number of libraries to address all current security advisories
• Warnings in the Dockerfile