feat(campaigns): add approval fields and CampaignModificationRequest model

backend/app/models/campaign.py

@@ -75,6 +75,13 @@ class Campaign(Base):
     )
     start_date = Column(DateTime, nullable=True)   # campaign won't activate before this date
     scheduled_at = Column(DateTime, nullable=True)
+    approved_by = Column(
+        UUID(as_uuid=True),
+        ForeignKey("users.id", ondelete="SET NULL"),
+        nullable=True,
+    )
+    approved_at = Column(DateTime, nullable=True)
+    rejection_reason = Column(Text, nullable=True)
     # Assign completed_at = Column(DateTime, nullable=True)
     completed_at = Column(DateTime, nullable=True)
     # Assign target_platform = Column(String, nullable=True)
@@ -229,3 +236,53 @@ class CampaignTest(Base):
         Index('ix_campaign_tests_campaign', 'campaign_id'),
         Index('ix_campaign_tests_test', 'test_id'),
     )
+
+
+class CampaignModificationRequest(Base):
+    """A lead's request to add or remove a test from an already-active campaign.
+
+    The underlying ``CampaignTest`` row is only created/deleted once a
+    manager approves the request — see ``approve_modification_request``
+    in ``campaign_crud_service.py``.
+    """
+    __tablename__ = "campaign_modification_requests"
+
+    id = Column(UUID(as_uuid=True), primary_key=True, default=uuid.uuid4)
+    campaign_id = Column(
+        UUID(as_uuid=True),
+        ForeignKey("campaigns.id", ondelete="CASCADE"),
+        nullable=False,
+    )
+    requested_by = Column(
+        UUID(as_uuid=True),
+        ForeignKey("users.id", ondelete="SET NULL"),
+        nullable=True,
+    )
+    action = Column(String, nullable=False)   # add_test, remove_test
+    test_id = Column(
+        UUID(as_uuid=True),
+        ForeignKey("tests.id", ondelete="CASCADE"),
+        nullable=False,
+    )
+    order_index = Column(Integer, nullable=True)
+    phase = Column(String, nullable=True)
+    justification = Column(Text, nullable=False)
+    status = Column(String, nullable=False, default="pending")   # pending, approved, rejected
+    reviewed_by = Column(
+        UUID(as_uuid=True),
+        ForeignKey("users.id", ondelete="SET NULL"),
+        nullable=True,
+    )
+    reviewed_at = Column(DateTime, nullable=True)
+    review_notes = Column(Text, nullable=True)
+    created_at = Column(DateTime(timezone=True), server_default=func.now())
+
+    campaign = relationship("Campaign")
+    test = relationship("Test")
+    requester = relationship("User", foreign_keys=[requested_by])
+    reviewer = relationship("User", foreign_keys=[reviewed_by])
+
+    __table_args__ = (
+        Index("ix_campaign_mod_requests_campaign", "campaign_id"),
+        Index("ix_campaign_mod_requests_status", "status"),
+    )