v6.3.0-beta.4

See full changelog here.

Commits:

• refactor STM queues (#1447)
• ntf server: record token invalidation reason, add date of the last token activity (#1449)
• agent: check ntf token status on registration (#1450)
• ntf server: additional statistics, new invalid token reasons (#1451)
• agent: refactor migrations (#1452)
• 6.3.0.4