feat: add bom.definitions

for #697

Signed-off-by: Hakan Dilek <hakandilek@gmail.com>

cyclonedx/model/bom.py

@@ -41,6 +41,7 @@
 from .bom_ref import BomRef
 from .component import Component
 from .contact import OrganizationalContact, OrganizationalEntity
+from .definition import DefinitionRepository, _DefinitionRepositoryHelper
 from .dependency import Dependable, Dependency
 from .license import License, LicenseExpression, LicenseRepository
 from .service import Service
@@ -72,6 +73,7 @@ def __init__(
         manufacturer: Optional[OrganizationalEntity] = None,
         # Deprecated as of v1.6
         manufacture: Optional[OrganizationalEntity] = None,
+        definitions: Optional[DefinitionRepository] = None,
     ) -> None:
         self.timestamp = timestamp or _get_now_utc()
         self.tools = tools or []  # type:ignore[assignment]
@@ -88,6 +90,7 @@ def __init__(
                 '`bom.metadata.manufacture` is deprecated from CycloneDX v1.6 onwards. '
                 'Please use `bom.metadata.component.manufacturer` instead.',
                 DeprecationWarning)
+        self.definitions = definitions
 
     @property
     @serializable.type_mapping(serializable.helpers.XsdDateTime)
@@ -282,6 +285,23 @@ def properties(self) -> 'SortedSet[Property]':
     def properties(self, properties: Iterable[Property]) -> None:
         self._properties = SortedSet(properties)
 
+    @property
+    @serializable.type_mapping(_DefinitionRepositoryHelper)
+    @serializable.view(SchemaVersion1Dot6)
+    @serializable.xml_sequence(90)
+    def definitions(self) -> Optional[DefinitionRepository]:
+        """
+        The repository for definitions
+
+        Returns:
+            `DefinitionRepository`
+        """
+        return self._definitions
+
+    @definitions.setter
+    def definitions(self, definitions: DefinitionRepository) -> None:
+        self._definitions = definitions
+
     def __eq__(self, other: object) -> bool:
         if isinstance(other, BomMetaData):
             return hash(other) == hash(self)