[DOP-28075] Add dataset tags to entities documentation

Author: dolfinus

docs/entities/index.rst

@@ -112,6 +112,7 @@ That's why the information about datasets is very limited:
 - ``location: Location`` - Location where data is actually stored in, like RDMBS instance or cluster.
 - ``name: str`` - qualified name of Dataset, like ``mydb.myschema.mytable`` or ``/app/warehouse/hive/managed/myschema.df/mytable``
 - ``schema: Schema | None`` - schema of dataset.
+- ``tags: list[Tag]`` - tags of dataset.
 
 .. image:: dataset_list.png
 
@@ -145,6 +146,18 @@ It contains following fields:
 
 .. image:: dataset_schema.png
 
+Dataset tags
+^^^^^^^^^^^^
+
+Dataset can have multiple tags which are arbitrary ``key: value`` pairs.
+
+- ``id: int`` - tag identifier
+- ``name: str`` - tag name, usually in format ``source.name``, e.g. ``airflow.tag``,  ``company.team``
+- ``values: list[TagValue]`` - tag values bound to dataset:
+
+  - ``id: int`` - tag value identifier
+  -  ``value: str`` - tag value, e.g. ``production``, ``Some team``
+
 Job
 ~~~
 

docs/reference/database/structure.rst

@@ -156,6 +156,26 @@ Database structure
         fingerprint: uuid(v5)
     }
 
+    entity tag {
+        * id: bigint
+        ----
+        * name: varchar(64)
+    }
+
+    entity tag_value {
+        * id: bigint
+        ----
+        * tag_id: bigint
+        * value: varchar(256)
+    }
+
+    entity dataset_tag {
+        * id: bigint
+        ----
+        * dataset_id: bigint
+        * tag_value_id: bigint
+    }
+
     entity personal_token {
         * id: uuid(v7)
         ----
@@ -201,6 +221,9 @@ Database structure
     column_lineage "target_dataset_id" ||--o{ dataset
     column_lineage "fingerprint" ||--o{ dataset_column_relation
 
+    tag_value ||--o{ tag
+    dataset_tag ||--o{ tag_value
+
     personal_token ||--o{ user
 
     @enduml