refactor: make headframe_part_number Optional[] (#1654)

* optional

* docs

Author: saskiad

docs/source/components/surgery_procedures.md

@@ -112,7 +112,7 @@ Description of headframe procedure
 |-------|------|-------------|
 | `protocol_id` | `Optional[str]` | Protocol ID (DOI for protocols.io) |
 | `headframe_type` | `str` | Headframe type  |
-| `headframe_part_number` | `str` | Headframe part number  |
+| `headframe_part_number` | `Optional[str]` | Headframe part number  |
 | `headframe_material` | Optional[[HeadframeMaterial](#headframematerial)] | Headframe material  |
 | `well_part_number` | `Optional[str]` | Well part number  |
 | `well_type` | `Optional[str]` | Well type  |

src/aind_data_schema/components/surgery_procedures.py

@@ -154,7 +154,7 @@ class Headframe(DataModel):
 
     protocol_id: Optional[str] = Field(default=None, title="Protocol ID", description="DOI for protocols.io")
     headframe_type: str = Field(..., title="Headframe type")
-    headframe_part_number: str = Field(..., title="Headframe part number")
+    headframe_part_number: Optional[str] = Field(default=None, title="Headframe part number")
     headframe_material: Optional[HeadframeMaterial] = Field(default=None, title="Headframe material")
     well_part_number: Optional[str] = Field(default=None, title="Well part number")
     well_type: Optional[str] = Field(default=None, title="Well type")