db: Replace use of reverse cascades

Resolve the following RemovedIn20Warning warning:

  "SecretStoreMetadatum" object is being merged into a Session along the
  backref cascade path for relationship "Secret.secret_store_metadata";
  in SQLAlchemy 2.0, this reverse cascade will not take place.  Set
  cascade_backrefs to False in either the relationship() or backref()
  function for the 2.0 behavior; or to set globally for the whole
  Session, set the future=True flag

In effect, this means if you have a model that refers to another model,
creating/saving the former will no longer create/save the latter. We
have only one instance of this error - the error message above - and in
our case we are explicitly saving the 'Secret' instance before saving
the 'SecretStoreMetadatum' instance. As such, we can opt-in to the 2.0
behavior with no further changes. We do this for all relationships to be
safe.

More information on this issue can be found at [1].

[1] https://groups.google.com/g/sqlalchemy/c/VoY-qEiJA3U?pli=1

Change-Id: I4b4fa4c224113863643e16153478183447796146
Signed-off-by: Stephen Finucane <stephenfin@redhat.com>

barbican/model/models.py

@@ -307,18 +307,21 @@ class Secret(BASE, SoftDeleteMixIn, ModelBase):
         "SecretStoreMetadatum",
         collection_class=col.attribute_mapped_collection('key'),
         backref="secret",
-        cascade="all, delete-orphan")
+        cascade="all, delete-orphan",
+        cascade_backrefs=False)
 
     secret_user_metadata = orm.relationship(
         "SecretUserMetadatum",
         collection_class=col.attribute_mapped_collection('key'),
         backref="secret",
-        cascade="all, delete-orphan")
+        cascade="all, delete-orphan",
+        cascade_backrefs=False)
 
     consumers = orm.relationship(
         "SecretConsumerMetadatum",
         backref="secret",
-        cascade="all, delete-orphan")
+        cascade="all, delete-orphan",
+        cascade_backrefs=False)
 
     def __init__(self, parsed_request=None, check_exc=True):
         """Creates secret from a dict."""
@@ -573,13 +576,15 @@ class Order(BASE, SoftDeleteMixIn, ModelBase):
         "OrderPluginMetadatum",
         collection_class=col.attribute_mapped_collection('key'),
         backref="order",
-        cascade="all, delete-orphan")
+        cascade="all, delete-orphan",
+        cascade_backrefs=False)
 
     order_barbican_metadata = orm.relationship(
         "OrderBarbicanMetadatum",
         collection_class=col.attribute_mapped_collection('key'),
         backref="order",
-        cascade="all, delete-orphan")
+        cascade="all, delete-orphan",
+        cascade_backrefs=False)
 
     def __init__(self, parsed_request=None, check_exc=True):
         """Creates a Order entity from a dict."""
@@ -910,7 +915,8 @@ class CertificateAuthority(BASE, ModelBase):
         'CertificateAuthorityMetadatum',
         collection_class=col.attribute_mapped_collection('key'),
         backref="ca",
-        cascade="all, delete-orphan"
+        cascade="all, delete-orphan",
+        cascade_backrefs=False,
     )
 
     def __init__(self, parsed_ca_in=None, check_exc=True):
@@ -1134,8 +1140,10 @@ class SecretACL(BASE, ModelBase):
         'Secret', backref=orm.backref('secret_acls', lazy=False))
 
     acl_users = orm.relationship(
-        'SecretACLUser', backref=orm.backref('secret_acl', lazy=False),
-        cascade="all, delete-orphan")
+        'SecretACLUser',
+        backref=orm.backref('secret_acl', lazy=False),
+        cascade="all, delete-orphan",
+        cascade_backrefs=False)
 
     __table_args__ = (sa.UniqueConstraint(
         'secret_id', 'operation', name='_secret_acl_operation_uc'),)
@@ -1210,8 +1218,10 @@ class ContainerACL(BASE, ModelBase):
         'Container', backref=orm.backref('container_acls', lazy=False))
 
     acl_users = orm.relationship(
-        'ContainerACLUser', backref=orm.backref('container_acl', lazy=False),
-        cascade="all, delete-orphan")
+        'ContainerACLUser',
+        backref=orm.backref('container_acl', lazy=False),
+        cascade="all, delete-orphan",
+        cascade_backrefs=False)
 
     __table_args__ = (sa.UniqueConstraint(
         'container_id', 'operation', name='_container_acl_operation_uc'),)

barbican/tests/fixture.py

@@ -190,13 +190,6 @@ class WarningsFixture(fixtures.Fixture):
             category=sqla_exc.SADeprecationWarning,
         )
 
-        warnings.filterwarnings(
-            'ignore',
-            module='barbican',
-            message=r'".*" object is being merged into a Session along .*',
-            category=sqla_exc.SADeprecationWarning,
-        )
-
         warnings.filterwarnings(
             'ignore',
             module='barbican',