feat: add governed LDIF contact imports

src/govoplan_addresses/backend/import_schemas.py

@@ -6,7 +6,7 @@ from typing import Any, Literal
 from pydantic import BaseModel, ConfigDict, Field, model_validator
 
 
-AddressImportFormat = Literal["csv", "xlsx"]
+AddressImportFormat = Literal["csv", "xlsx", "ldif"]
 AddressImportScope = Literal["user", "group", "tenant", "system"]
 
 IMPORT_TARGET_FIELDS = frozenset(
@@ -41,6 +41,7 @@ class AddressImportConfiguration(BaseModel):
     duplicate_source_key_policy: Literal["reject", "first", "last"] = "reject"
     existing_contact_policy: Literal["update", "ignore", "reject"] = "update"
     blank_value_policy: Literal["ignore", "clear", "reject"] = "ignore"
+    ldif_change_record_policy: Literal["reject", "ignore", "treat_add_as_entry"] = "reject"
     locale: str | None = Field(default=None, max_length=35)
     default_tags: list[str] = Field(default_factory=list, max_length=100)
     max_rows: int = Field(default=10_000, ge=1, le=10_000)