feat: add campaign copying scheduling and residual handling

src/govoplan_campaign/backend/campaign/models.py

@@ -468,6 +468,30 @@ class AttachmentBasePathConfig(StrictModel):
     source: str | None = None
 
 
+class ResidualFileMode(StrEnum):
+    NONE = "none"
+    REPORT = "report"
+    ATTACH = "attach"
+
+
+class ResidualFileDispositionConfig(StrictModel):
+    mode: ResidualFileMode = ResidualFileMode.NONE
+    recipient: RecipientConfig | None = None
+    subject: str = "Unassigned files in campaign {{local:campaign_name}}"
+    text: str = (
+        "The campaign build found {{local:residual_file_count}} file(s) that "
+        "were not assigned to a recipient.\n\n{{local:residual_file_list}}"
+    )
+
+    @model_validator(mode="after")
+    def require_recipient_for_routing(self) -> "ResidualFileDispositionConfig":
+        if self.mode != ResidualFileMode.NONE and self.recipient is None:
+            raise ValueError(
+                "Residual-file report or attachment routing requires a recipient."
+            )
+        return self
+
+
 class AttachmentConfig(StrictModel):
     id: str | None = None
     label: str | None = None
@@ -509,6 +533,9 @@ class AttachmentsConfig(StrictModel):
     global_: list[AttachmentConfig] = Field(default_factory=list, alias="global")
     missing_behavior: Behavior = Behavior.WARN
     ambiguous_behavior: Behavior = Behavior.ASK
+    residual_files: ResidualFileDispositionConfig = Field(
+        default_factory=ResidualFileDispositionConfig
+    )
 
     @model_validator(mode="after")
     def normalize_send_without_attachments_behavior(self) -> "AttachmentsConfig":