feat(FCL-499): add new FCLID identifier class

This allows us to store and create SQID-based FCLIDs, using the document sequence counter in MarkLogic

src/caselawclient/models/identifiers/fclid.py

@@ -0,0 +1,48 @@
+import re
+from typing import TYPE_CHECKING
+
+from sqids import Sqids
+
+from . import Identifier, IdentifierSchema
+
+if TYPE_CHECKING:
+    from caselawclient.Client import MarklogicApiClient
+
+
+VALID_FCLID_PATTERN = re.compile(r"^[bcdfghjkmnpqrstvwxyz23456789]{4,}$")
+
+FCLID_MINIMUM_LENGTH = 8
+FCLID_ALPHABET = "bcdfghjkmnpqrstvwxyz23456789"
+
+sqids = Sqids(
+    min_length=FCLID_MINIMUM_LENGTH,
+    alphabet=FCLID_ALPHABET,
+)
+
+
+class FindCaseLawIdentifierSchema(IdentifierSchema):
+    """
+    Identifier schema describing a Find Case Law Identifier.
+    """
+
+    name = "Find Case Law Identifier"
+    namespace = "fclid"
+
+    @classmethod
+    def validate_identifier(cls, value: str) -> bool:
+        return bool(VALID_FCLID_PATTERN.match(value))
+
+    @classmethod
+    def compile_identifier_url_slug(cls, value: str) -> str:
+        return "tna." + value
+
+    @classmethod
+    def mint(cls, api_client: "MarklogicApiClient") -> "FindCaseLawIdentifier":
+        """Generate a totally new Find Case Law identifier."""
+        next_sequence_number = api_client.get_next_document_sequence_number()
+        new_identifier = sqids.encode([next_sequence_number])
+        return FindCaseLawIdentifier(value=new_identifier)
+
+
+class FindCaseLawIdentifier(Identifier):
+    schema = FindCaseLawIdentifierSchema

src/caselawclient/models/identifiers/unpacker.py

@@ -3,9 +3,11 @@
 from lxml import etree
 
 from . import IDENTIFIER_UNPACKABLE_ATTRIBUTES, Identifier, Identifiers, InvalidIdentifierXMLRepresentationException
+from .fclid import FindCaseLawIdentifier
 from .neutral_citation import NeutralCitationNumber
 
 IDENTIFIER_NAMESPACE_MAP: dict[str, type[Identifier]] = {
+    "fclid": FindCaseLawIdentifier,
     "ukncn": NeutralCitationNumber,
 }