feat: adapt for PostgreSQL

Created by: melanger

• renamed columns idpId and spId (BREAKING CHANGE), because camelCase column names require escaping in postgreSQL
• added postgreSQL specific syntax where needed, or general SQL syntax instead of MySQL-specific
  • changed DELETE statement in aggregation from inner join to a regular delete with subquery
  • changed IFNULL to COALESCE
  • changed YEAR() etc. to EXTRACT(YEAR FROM ...) etc.
• fixed JavaScript to handle dates with time zones
• added migrations scripts for altering database tables from v5