Make properties and type optional for BuildModules

Neither field is listed as `required` in the buildinfo schema at
https://github.com/jfrog/build-info-go/blob/main/buildinfo-schema.json

These were also not present in a live instance of Artifactory, causing
validation errors for a BuildInfo

Author: Eero Aaltonen

pyartifactory/models/build.py

@@ -63,8 +63,8 @@ class BuildArtifact(BaseModel):
 class BuildModules(BaseModel):
     """Models artifactory's build modules."""
 
-    properties: Dict[str, str]
-    type: str
+    properties: Optional[Dict[str, str]] = None
+    type: Optional[str] = None
     id: str
     artifacts: List[BuildArtifact]