feat(campaigns): add pending_approval state to campaign domain entity

backend/app/domain/entities/campaign.py

@@ -33,6 +33,8 @@ class CampaignStatus(str, enum.Enum):
 
     # Assign draft = "draft"
     draft = "draft"
+    # Assign pending_approval = "pending_approval"
+    pending_approval = "pending_approval"
     # Assign active = "active"
     active = "active"
     # Assign completed = "completed"
@@ -57,7 +59,8 @@ class CampaignType(str, enum.Enum):
 
 # Assign VALID_TRANSITIONS = {
 VALID_TRANSITIONS: dict[CampaignStatus, list[CampaignStatus]] = {
-    CampaignStatus.draft: [CampaignStatus.active],
+    CampaignStatus.draft: [CampaignStatus.pending_approval, CampaignStatus.active],
+    CampaignStatus.pending_approval: [CampaignStatus.active, CampaignStatus.draft],
     CampaignStatus.active: [CampaignStatus.completed],
     CampaignStatus.completed: [CampaignStatus.archived],
     CampaignStatus.archived: [],
@@ -132,6 +135,49 @@ class CampaignEntity:
         # Assign self.status = CampaignStatus.active
         self.status = CampaignStatus.active
 
+    def submit_for_approval(self) -> None:
+        """Transition the campaign from ``draft`` to ``pending_approval``.
+
+        Returns:
+            None
+        """
+        if not self.can_transition_to(CampaignStatus.pending_approval):
+            raise InvalidStateTransition(
+                self.status.value, CampaignStatus.pending_approval.value,
+                [s.value for s in VALID_TRANSITIONS[self.status]],
+            )
+        if self.test_count == 0:
+            raise BusinessRuleViolation(
+                "Campaign must have at least one test to submit for approval"
+            )
+        self.status = CampaignStatus.pending_approval
+
+    def approve(self) -> None:
+        """Transition the campaign from ``pending_approval`` to ``active``.
+
+        Returns:
+            None
+        """
+        if self.status != CampaignStatus.pending_approval:
+            raise InvalidStateTransition(
+                self.status.value, CampaignStatus.active.value,
+                [s.value for s in VALID_TRANSITIONS[self.status]],
+            )
+        self.status = CampaignStatus.active
+
+    def reject(self) -> None:
+        """Transition the campaign from ``pending_approval`` back to ``draft``.
+
+        Returns:
+            None
+        """
+        if not self.can_transition_to(CampaignStatus.draft):
+            raise InvalidStateTransition(
+                self.status.value, CampaignStatus.draft.value,
+                [s.value for s in VALID_TRANSITIONS[self.status]],
+            )
+        self.status = CampaignStatus.draft
+
     # Define function complete
     def complete(self) -> None:
         """Transition the campaign from ``active`` to ``completed``.