Add converter to dedupe lists in TimdexRecord

Why these changes are being introduced:
* Reduce duplication of data for TimdexRecord attributes
of list type.

How this addresses that need:
* Create an attrs converter function to dedupe list of items
* Add __hash__ methods for custom classes
* Apply dedupe methods to derived fields

Side effects of this change:
* Deduplication is highly likely to result in diffs
when comparing transformed records before and after this
change. That said, we are improving our transformation
pipeline by removing duplicated data.

Relevant ticket(s):
* https://mitlibraries.atlassian.net/browse/TIMX-332

transmogrifier/models.py

@@ -35,6 +35,12 @@ def list_of(item_type: Any) -> Callable:  # noqa: ANN401
     )
 
 
+def dedupe(item_list: list | None) -> list:
+    if item_list is None:
+        return item_list
+    return list(set(item_list))
+
+
 def not_empty(
     _instance: "TimdexRecord", attribute: "attrs.Attribute", value: "list"
 ) -> None:
@@ -77,6 +83,9 @@ class Date:
     )
     value: str | None = field(default=None, validator=optional(instance_of(str)))
 
+    def __hash__(self) -> int:
+        return hash((self.kind, self.note, self.range, self.value))
+
 
 @define
 class Funder:
@@ -120,6 +129,9 @@ class Location:
     kind: str | None = field(default=None, validator=optional(instance_of(str)))
     geoshape: str | None = field(default=None, validator=optional(instance_of(str)))
 
+    def __hash__(self) -> int:
+        return hash((self.value, self.kind, self.geoshape))
+
 
 @define
 class Note:
@@ -169,12 +181,16 @@ class TimdexRecord:
     )
     call_numbers: list[str] | None = field(default=None, validator=optional(list_of(str)))
     citation: str | None = field(default=None, validator=optional(instance_of(str)))
-    content_type: list[str] | None = field(default=None, validator=optional(list_of(str)))
+    content_type: list[str] | None = field(
+        default=None, converter=dedupe, validator=optional(list_of(str))
+    )
     contents: list[str] | None = field(default=None, validator=optional(list_of(str)))
     contributors: list[Contributor] | None = field(
         default=None, validator=optional(list_of(Contributor))
     )
-    dates: list[Date] | None = field(default=None, validator=optional(list_of(Date)))
+    dates: list[Date] | None = field(
+        default=None, converter=dedupe, validator=optional(list_of(Date))
+    )
     edition: str | None = field(default=None, validator=optional(instance_of(str)))
     file_formats: list[str] | None = field(default=None, validator=optional(list_of(str)))
     format: str | None = field(default=None, validator=optional(instance_of(str)))
@@ -191,7 +207,7 @@ class TimdexRecord:
     links: list[Link] | None = field(default=None, validator=optional(list_of(Link)))
     literary_form: str | None = field(default=None, validator=optional(instance_of(str)))
     locations: list[Location] | None = field(
-        default=None, validator=optional(list_of(Location))
+        default=None, converter=dedupe, validator=optional(list_of(Location))
     )
     notes: list[Note] | None = field(default=None, validator=optional(list_of(Note)))
     numbering: str | None = field(default=None, validator=optional(instance_of(str)))