Merge upstream changes

[brandonscholten]

• The AppCache class has been rewritten to use an SQLite database instead of reading and writing from JSON in an effort to reduce memory usage.
• Saving identifiers is now optional, and users are able to specify the name of a database to save identifiers to. This involved changing the format of the URL used to tag identifiers and adding a /probe route which allows users to check if a database already exists
• updated README to document this functionality
• added restart: always to the docker compose file.
• save the time to takes to tag an identifier in the database.
• account for the context of the identifier when saving identifiers to the database.