tickets are also in delivery table

InventoryListBrain does not need a getQuantity method which returns something
else that the total_quantity on this brain, this is just confusing (and using
movement table)

The idea is to use Inventory API instead.

Also, movement with 0 price where ignored by omit_asset_increase /
omit_asset_decrease
Signed-off-by: Aurélien Calonne <aurel@nexedi.com>

Signed-off-by: Aurélien Calonne <aurel@nexedi.com>

To migrate, run:
alter table stock add column payment_request_uid bigint unsigned after funding_uid, add index payment_request_uid (payment_request_uid);
alter table inventory_stock add column payment_request_uid bigint unsigned after funding_uid;

To migrate, run:
alter table stock add column funding_uid bigint unsigned after payment_uid, add index funding_uid (funding_uid);
alter table inventory_stock add column funding_uid bigint unsigned after payment_uid;

This hurts performances a lot.

... instead of relying on automatic migration.

This fixes TestCMFActivity.test_connection_sortkey on Zope 2.13

Use already existing system preference and created accessor rather than hard coded value which was different from
default for the system preference
This can lead to different cache ids generated for same content by different
parts of the code -> duplication of same data in cache backend.

When a ZODB connection is closed, it usually returns to a ZODB pool and may be
reused by another thread. If the SQL connection was open and is still in ZODB
cache, the _v_database_connection attribute is still there:
ActivityConnection.connect() is not called and a new instance of ZMySQLDA.db.DB
is created for the new thread without initializing its sort key.