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…rSchemaSubscriber (alli83)

This PR was merged into the 6.3 branch.

Discussion
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[HttpFoundation] inject SessionHandler in PdoSessionHandlerSchemaSubscriber

| Q             | A
| ------------- | ---
| Branch?       | 6.3
| Bug fix?      | yes
| New feature?  | no
| Deprecations? | no
| License       | MIT
| Doc PR        |  I'm working on it

following the PR #48059.

In #48059, it works only if you put the handler explicitly to PdoSessionHandler in the configuration (handler_id) but it stops working if the session is defined by the factory and we can't use it as follow:
````
handler_id: '%env(resolve:DATABASE_URL)%'
`````

Linked to DoctrineBundle PR doctrine/DoctrineBundle#1623

Also imho, I think the second argument of configureSchema inPdoSessionHandler should be optional and set to return true if not defined  since the function is public eg. one wants to add the table to the Schema.

Commits
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9aded06 [HttpFoundation] inject SessionHandler in PdoSessionHandlerSchemaSubscriber