Separated scheme loading from main thread.

What steps will reproduce the problem?

Schema loading on the main thread is problematic in several ways (like yii2):

• block main thread, increase response delay
  • this is particularly problematic as databases do not have an RFC on how long the schema loading response in 1ms, 100ms, 10sec... for example https://github.com/yiisoft/yii2/issues/17444
• not really suitable for event based updates (for example after deploy)
• cache TTL problems
  • with large TTL, the change is noticed slowly
  • with small TTL, a lot of updates are unnecessary

What is the expected result?

• The schema load can be called at any time, regardless of the main thread

I suggests

The best solution would be to generate the table schema to PHP code (for example one class/table).

• not require cache (no connection and loading delay)
• generation is event-based (for example, after generating the yii3 configuration)

No files, tests, or entry points are named. Start by locating the current schema-loading path in the db repository and determine how it is invoked; done would mean schema loading can occur independently of the main thread and the proposed generated PHP schema approach is defined and verified.