Update project serializer to include publish_date, doi, version (#2378)

We have an API at
`http://localhost:8000/api/v1/project/published/search` that allows
users to export metadata about published projects.

The API is potentially useful for people who are developing tools that
interface with PhysioNet content (e.g. the MEDS project:
https://github.com/Medical-Event-Data-Standard.

The metadata returned from queries is defined in
`PublishedProjectSerializer`. This pull request updates this serializer
to include the following fields:

- `version` (important, because otherwise a search returns what look
like duplicate results, one result for each version).
- `core_doi`
- `version_doi` -> (from `doi`)
- `is_latest_version`
- `short_description`
- `publish_date`

Also adds a citation string to the `ProjectVersionsSerializer` method.

Author: Chrystinne

physionet-django/export/serializers.py

@@ -23,11 +23,20 @@ class Meta:
 class PublishedProjectSerializer(serializers.ModelSerializer):
     license = LicenseSerializer()
     dua = DUASerializer()
+    publish_date = serializers.SerializerMethodField()
+    core_doi = serializers.SerializerMethodField()
+    version_doi = serializers.SerializerMethodField()
 
     class Meta:
         model = PublishedProject
         fields = (
             'slug',
+            'version',
+            'core_doi',
+            'version_doi',
+            'is_latest_version',
+            'short_description',
+            'publish_date',
             'title',
             'abstract',
             'license',
@@ -36,17 +45,32 @@ class Meta:
             'compressed_storage_size',
         )
 
+    def get_publish_date(self, obj):
+        return obj.publish_datetime.date() if obj.publish_datetime else None
+
+    def get_core_doi(self, obj):
+        return obj.core_project.doi if hasattr(obj, 'core_project') else None
+
+    def get_version_doi(self, obj):
+        return obj.doi
+
 
 class ProjectVersionsSerializer(serializers.ModelSerializer):
+    citation = serializers.SerializerMethodField()
+
     class Meta:
         model = PublishedProject
         fields = (
             'slug',
             'title',
             'version',
             'abstract',
+            'citation',
         )
 
+    def get_citation(self, obj):
+        return obj.citation_text(style="Vancouver")
+
 
 class PublishedProjectDetailSerializer(serializers.ModelSerializer):
     license = LicenseSerializer()