Unify and refactor exception handling in framework and addons.
The generic `except_osv` is now deprecated, and replaced by more specialized exception subtypes:
- `UserError` (renamed from Warning, as it conflicts with the built-in `Warning`) raised when a non-technical error occurs during a business operation. It could be a missing information in the data provided by the user, or a misconfiguration.
- `AccessError`: raised when any operation is denied because the user conducting it does not have the required access rights.
- `AccessDenied`: raised when an operation that requires authenticated access is attempted via an unauthenticated request.
- `MissingError`: raised when an operation is attempted on a record that does not exist.
- `ValidationError`: raised when an operation violates a SQL or Python constraint.
- All other exceptions are internal errors due to a system problem or bug, and raised untouched to the client-side, which should display a traceback.
All exceptions take a single message argument.
The `test_exceptions` module has been updated to showcase both new and old (deprecated) exceptions.
A great many old `except_osv` had a useless title with "Error!" or "Warning", those have been removed, as this is handled by the client-side widget that displays the messages.
This commit introduces a more consistent policy for logging errors and warnings:
- All messages that do not require administrator attention should be logged at INFO level or lower. This includes all errors that are notified to the user in a friendly manner, even for access right problems or validation errors during business operations.
- All messages that indicate a likely misconfiguration or malicious use by the users should be logged at WARNING level, as they typically require administrator attention.
- All other unhandled internal errors cannot typically be handled by the user and should be logged at ERROR or higher level, as they require immediate administrator attention.
1. The merge of the "email_template" module into the "mail" module.
2. The send action of the mass mailing has been moved from the frontend to a cron, because it was too slow to send over 10,000 mails (the user's browser was blocked for 15 - 20 minutes). Mass mailings have now their own process in the kanban view.
3. Mails sent from the mail form are sent immediatly instead of from the mail queue (for instance, when you go to sales > customers > list view > select 2 -3 customers > More > Partner Mass Mailing).
4. Users have now the choice from which mailing list they want to unsubscribe when they click on the unsubscribe link at the bottom of the mail.
5. Mass mailings inherit from their campaign UTMs and mass mailing campaigns are linked to an UTM campaign.
6. Many little improvements
