Wimms

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- Removed "service acceptance" flags and the related metadata table.
- Added tracking of optional "generation number" for each user account,
which can be used to more quickly detect password change events.
- Added tracking of optional "client state" string for each user account,
which can be used to force node reallocation when client state changes.

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- Added a metadata table which is able to store information related to the user
and service.

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- allocated_node will just return an existing node.

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- added the pool_reset_on_return option

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- initial release