We have decided to prefix callbacks in the Realm configuration with on. Before this breaking change, we need to issue a deprecation warning (API doc and TS defs).

Callback provided by a user, which is called on events (and returns void) should be prefixed with "on".

We have identified the following callbacks (there might be more ...):

• migration (onMigration)
• shouldCompactOnLaunch (shouldCompact)
• error (onError)
• clientResetBefore (onBefore)
  {}{ sync: { clientReset: { onBefore() { /**/ } } } }{}
• clientResetAfter (onAfter)
• validateCallback (validateCertificates)