[2.3][Feature] Add support for configurable invoice sequence scopes

[tomkalon]

Q	A
Branch?	2.3
Bug fix?	no
New feature?	yes
BC breaks?	yes
Related tickets	#131
License	MIT

Summary

Adds configurable invoice number sequence scoping (global / monthly / annually, defaulting to global for full backward compatibility) and closes a race condition that could produce duplicated invoice numbers.

• New SequenceScopeResolverInterface with Global/Monthly/Annually resolvers, pluggable via sylius_invoicing.sequence_scope_resolver tag.
• Unique DB constraints: one invoice number across the whole system, one sequence counter per scope period.
• InvoiceCreator now persists the invoice before writing its PDF, so a duplicate number fails on the DB constraint instead of silently overwriting a file.
• Migrations provided for both MySQL and PostgreSQL.
• Behat coverage for all three scopes, duplicate prevention, and invoice file recovery.

Config

New sequence.scope option under sylius_invoicing, defaults to global:

sylius_invoicing:
    sequence:
        scope: global # one of "global", "monthly", "annually"

• global — one ever-increasing counter for the whole store, never reset (previous behavior).
• monthly — a counter per year/month, reset on the 1st of every month.
• annually — a counter per year, reset on the 1st of January.

All three share the same Y/m/index number format — only the reset behavior differs.

Custom scopes can be added by registering a service implementing SequenceScopeResolverInterface,
tagged with sylius_invoicing.sequence_scope_resolver, and setting its name as scope.

BC breaks

Full details in UPGRADE-2.3.md.

• InvoiceSequenceInterface gained getType()/setType(), getYear()/setYear(), getMonth()/setMonth()
  and the SCOPE_GLOBAL/SCOPE_MONTHLY/SCOPE_ANNUALLY constants. Any custom class implementing this interface
  directly (rather than extending the provided InvoiceSequence) will fail to compile until it adds these methods.

• InvoiceCreator now persists the invoice before writing its PDF file (previously the other way round), and
  no longer catches ORMException around the persist call. A duplicated invoice number now fails loudly with a DB
  constraint violation propagated to the caller, instead of being silently swallowed while the PDF file was removed.
  Callers relying on createInvoice() never throwing must be updated to handle the exception.

• SequentialInvoiceNumberGenerator constructor gained two new optional arguments ($scopeResolvers, $scope).
  Not a breaking change — omitting $scopeResolvers triggers a deprecation and falls back to the built-in resolvers.

  Add support for configurable invoice sequence scopes #429