Fix inconsistent text field aliasing in vector and hybrid search queries

[davide-evangelisti-prom]

Summary

This PR fixes bugs in the AzureCosmosDBNoSqlVectorSearch class where the text field alias is hardcoded as "description" instead of using the dynamically configured field name from self._vector_search_fields["text_field"].

Problem

When performing vector or hybrid searches without custom projection mapping, the code has two inconsistencies:

1. Line 900 (_generate_projection_fields method): The SQL projection hardcodes the alias as description:

   projection = f"{table}.id, {table}[@textKey] as description, ..."

2. Line 1007 (_execute_query method): The fallback when projection_mapping is not provided uses the hardcoded string "description" instead of the configured field name:

   text_key = "description"

This causes a mismatch between:

• The configured text field name in vector_search_fields["text_field"]
• The actual alias used in SQL queries
• The field name used to extract data from query results

Impact

• Potential KeyError at runtime when the configured text field name differs from "description"
• Inconsistent behavior between different search types (full-text search works correctly)

Changes

1. Updated line 900 to use the dynamic field name as alias
2. Updated line 1007 to use self._vector_search_fields["text_field"] instead of hardcoded "description"

[davide-evangelisti-prom]

Hi @nagkumar91 ,
Sorry if you’re not the right person to ask — if so, feel free to point me in the right direction.
Whenever possible, could someone take a look at this PR?
Thanks!