Implemented bulk upload by passing a json structure. Added delete all channels, groups and priorities

tests/utils/db_mocks.py

@@ -60,6 +60,9 @@ class MockChannelDB(MockBase):
         onupdate=lambda: datetime.now(timezone.utc),
     )
     group = relationship("MockGroup", back_populates="channels")
+    urls = relationship(
+        "MockChannelURL", back_populates="channel", cascade="all, delete-orphan"
+    )
 
 
 class MockChannelURL(MockBase):
@@ -77,6 +80,7 @@ class MockChannelURL(MockBase):
         default=lambda: datetime.now(timezone.utc),
         onupdate=lambda: datetime.now(timezone.utc),
     )
+    channel = relationship("MockChannelDB", back_populates="urls")
 
 
 def create_mock_priorities_and_group(db_session, priorities, group_name):