refactor: clarify ServerGroup relationships to Server and SharedServer (pgadmin-org#10076)

The Server and SharedServer models each declared a relationship named
'servers' that actually pointed at the parent ServerGroup, with backrefs
('server'/'sharedserver') providing the collections. The naming was the
inverse of what it modelled and made the call sites read oddly.

Redefine the relationships in the natural direction using explicit
back_populates: ServerGroup gains 'servers' and 'sharedservers'
collections (carrying the existing delete-orphan cascade), and Server and
SharedServer each gain a 'servergroup' reference. The two call sites that
read the group name are updated from server.servers.name to
server.servergroup.name accordingly.

This is a naming/modelling cleanup with no functional or schema change, so
no migration is required.

Author: Luiz K Matsumura

web/pgadmin/model/__init__.py

@@ -252,6 +252,20 @@ class ServerGroup(db.Model, UserScopedMixin):
     name = db.Column(db.String(128), nullable=False)
     __table_args__ = (db.UniqueConstraint('user_id', 'name'),)
 
+    servers = db.relationship(
+        'Server',
+        back_populates='servergroup',
+        lazy='select',
+        cascade=CASCADE_STR
+    )
+
+    sharedservers = db.relationship(
+        'SharedServer',
+        back_populates='servergroup',
+        lazy='select',
+        cascade=CASCADE_STR
+    )
+
     @property
     def serialize(self):
         """Return object data in easily serializable format"""
@@ -276,6 +290,11 @@ class Server(db.Model, UserScopedMixin):
         db.ForeignKey('servergroup.id'),
         nullable=False
     )
+    servergroup = db.relationship(
+        'ServerGroup',
+        back_populates='servers',
+        lazy='joined'
+    )
     name = db.Column(db.String(128), nullable=False)
     host = db.Column(db.String(128), nullable=True)
     port = db.Column(
@@ -293,11 +312,6 @@ class Server(db.Model, UserScopedMixin):
     role = db.Column(db.String(64), nullable=True)
     comment = db.Column(db.String(1024), nullable=True)
     discovery_id = db.Column(db.String(128), nullable=True)
-    servers = db.relationship(
-        'ServerGroup',
-        backref=db.backref('server', cascade=CASCADE_STR),
-        lazy='joined'
-    )
     db_res = db.Column(db.Text(), nullable=True)
     db_res_type = db.Column(db.String(32), default='databases')
     passexec_cmd = db.Column(db.Text(), nullable=True)
@@ -530,6 +544,11 @@ class SharedServer(db.Model, UserScopedMixin):
         db.ForeignKey('servergroup.id'),
         nullable=False
     )
+    servergroup = db.relationship(
+        'ServerGroup',
+        back_populates='sharedservers',
+        lazy='joined'
+    )
     name = db.Column(db.String(128), nullable=False)
     host = db.Column(db.String(128), nullable=True)
     port = db.Column(
@@ -546,11 +565,6 @@ class SharedServer(db.Model, UserScopedMixin):
     role = db.Column(db.String(64), nullable=True)
     comment = db.Column(db.String(1024), nullable=True)
     discovery_id = db.Column(db.String(128), nullable=True)
-    servers = db.relationship(
-        'ServerGroup',
-        backref=db.backref('sharedserver', cascade=CASCADE_STR),
-        lazy='joined'
-    )
     bgcolor = db.Column(db.String(10), nullable=True)
     fgcolor = db.Column(db.String(10), nullable=True)
     service = db.Column(db.Text(), nullable=True)

web/pgadmin/tools/schema_diff/__init__.py

@@ -307,10 +307,10 @@ def servers():
                 "connected": connected
             }
 
-            if server.servers.name in res:
-                res[server.servers.name].append(server_info)
+            if server.servergroup.name in res:
+                res[server.servergroup.name].append(server_info)
             else:
-                res[server.servers.name] = [server_info]
+                res[server.servergroup.name] = [server_info]
 
     except Exception as e:
         app.logger.exception(e)

web/pgadmin/tools/sqleditor/__init__.py

@@ -2434,7 +2434,7 @@ def get_new_connection_data(sgid=None, sid=None):
             manager = driver.connection_manager(server.id)
             conn = manager.connection()
             connected = conn.connected()
-            server_group_data[server.servers.name].append({
+            server_group_data[server.servergroup.name].append({
                 'label': server.name,
                 "value": server.id,
                 'image': server_icon_and_background(connected, manager,