feat: add discussions context to course blocks API (#29300)

Add a new course blocks transformer that adds discussion context for units.

lms/djangoapps/course_api/blocks/api.py

@@ -7,6 +7,7 @@ import lms.djangoapps.course_blocks.api as course_blocks_api
 from lms.djangoapps.course_blocks.transformers.access_denied_filter import AccessDeniedMessageFilterTransformer
 from lms.djangoapps.course_blocks.transformers.hidden_content import HiddenContentTransformer
 from openedx.core.djangoapps.content.block_structure.transformers import BlockStructureTransformers
+from openedx.core.djangoapps.discussions.transformers import DiscussionsTopicLinkTransformer
 from openedx.features.effort_estimation.api import EffortEstimationTransformer
 
 from .serializers import BlockDictSerializer, BlockSerializer
@@ -75,6 +76,10 @@ def get_blocks(
     include_gated_sections = 'show_gated_sections' in requested_fields
     include_has_scheduled_content = 'has_scheduled_content' in requested_fields
     include_special_exams = 'special_exam_info' in requested_fields
+    include_discussions_context = (
+        DiscussionsTopicLinkTransformer.EMBED_URL in requested_fields or
+        DiscussionsTopicLinkTransformer.EXTERNAL_ID in requested_fields
+    )
 
     if user is not None:
         transformers += course_blocks_api.get_course_block_access_transformers(user)
@@ -99,13 +104,16 @@ def get_blocks(
     if include_effort_estimation:
         transformers += [EffortEstimationTransformer()]
 
+    if include_discussions_context:
+        transformers += [DiscussionsTopicLinkTransformer()]
+
     transformers += [
         BlocksAPITransformer(
             block_counts,
             student_view_data,
             depth,
             nav_depth
-        )
+        ),
     ]
 
     # transform

lms/djangoapps/course_api/blocks/serializers.py

@@ -2,12 +2,12 @@
 Serializers for Course Blocks related return objects.
 """
 
-
 from django.conf import settings
 from rest_framework import serializers
 from rest_framework.reverse import reverse
 
 from lms.djangoapps.course_blocks.transformers.visibility import VisibilityTransformer
+from openedx.core.djangoapps.discussions.transformers import DiscussionsTopicLinkTransformer
 
 from .transformers.block_completion import BlockCompletionTransformer
 from .transformers.block_counts import BlockCountsTransformer
@@ -21,13 +21,14 @@ class SupportedFieldType:
     """
     Metadata about fields supported by different transformers
     """
+
     def __init__(
-            self,
-            block_field_name,
-            transformer=None,
-            requested_field_name=None,
-            serializer_field_name=None,
-            default_value=None
+        self,
+        block_field_name,
+        transformer=None,
+        requested_field_name=None,
+        serializer_field_name=None,
+        default_value=None
     ):
         self.transformer = transformer
         self.block_field_name = block_field_name
@@ -82,6 +83,8 @@ SUPPORTED_FIELDS = [
     SupportedFieldType(BlockCompletionTransformer.COMPLETION, BlockCompletionTransformer),
     SupportedFieldType(BlockCompletionTransformer.COMPLETE),
     SupportedFieldType(BlockCompletionTransformer.RESUME_BLOCK),
+    SupportedFieldType(DiscussionsTopicLinkTransformer.EXTERNAL_ID),
+    SupportedFieldType(DiscussionsTopicLinkTransformer.EMBED_URL),
 
     *[SupportedFieldType(field_name) for field_name in ExtraFieldsTransformer.get_requested_extra_fields()],
 ]
@@ -111,6 +114,7 @@ class BlockSerializer(serializers.Serializer):  # pylint: disable=abstract-metho
     """
     Serializer for single course block
     """
+
     def _get_field(self, block_key, transformer, field_name, default):
         """
         Get the field value requested.  The field may be an XBlock field, a