Kinto

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**Internal changes**

- Upgraded the kinto-admin to version `1.15.1 <https://github.com/Kinto/kinto-admin/releases/tag/v1.15.1>`_
- Upgraded newrelic to `2.106.1.88 <https://docs.newrelic.com/docs/release-notes/agent-release-notes/python-release-notes/python-agent-2106188>`_

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**New features**

- Add Openid connect support (939, 1425). See `demo <https://github.com/leplatrem/kinto-oidc-demo>`_
- Account plugin now caches authentication verification (1413)

**Bug fixes**

- Fix missing principals from user info in root URL when default bucket plugin is enabled (fixes 1495)
- Fix crash in Postgresql when the value of url param is empty (fixes 1305)

**Internal Changes**

- Upgraded the kinto-admin to version `1.15.0 <https://github.com/Kinto/kinto-admin/releases/tag/v1.15.0>`_

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**Bug fixes**

- Restore "look before you leap" behavior in the Postgres storage
backend create() method to check whether a record exists before
running the INSERT query (1487). This check is "optimistic" in the sense
that we can still fail to INSERT after the check succeeded, but it
can reduce write load in configurations where there are a lot of
create()s (i.e. when using the default_bucket plugin).

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**Bug fixes**

- Allow inherited resources to set a custom model instance before instantiating (fixes 1472)
- Fix collection timestamp retrieval when the stack is configured as readonly (fixes 1474)

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**Bug fixes**

- Optimize the PostgreSQL permission backend's
``delete_object_permissions`` function in the case where we are only
matching one object_id (or object_id prefix).

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**Bug fixes**

- Flushing a server no longer breaks migration of the storage backend
(1460). If you have ever flushed a server in the past, migration
may be broken. This version of Kinto tries to guess what version of
the schema you're running, but may guess wrong. See
https://github.com/Kinto/kinto/wiki/Schema-versions for some
additional information.

**Internal changes**

- We now allow migration of the permission backend's schema.

**Operational concerns**

- *The schema for the Postgres permission backend has changed.* This
changes another ID column to use the "C" collation, which should
speed up the `delete_object_permissions` query when deleting a
bucket.