WIP: Render database schema using Mermaid.js

Still need to:
* Move mermaid.js to static files
* Make template for mermaid wrapper
* Create new page for SQL viewer then add explorer

app.py

@@ -469,6 +469,22 @@ def delete_exercise(exercise_id):
     db.exercises.delete_exercise(exercise_id)
     return ""
 
+@ app.route("/sql_schema", methods=['GET'])
+def get_sql_schema():
+    schema_info = db.sql_viewer.get_schema_info()
+    mermaid_code = db.sql_viewer.generate_mermaid_er(schema_info)
+    html_content = f'''
+    <div class="overflow-auto" style="max-height: 80vh;">
+        <div class="mermaid" style="opacity: 0;"
+             _="on load
+                 mermaid.init(undefined, this)
+                 set me.style.opacity to '1'">
+{mermaid_code}
+        </div>
+    </div>
+    '''
+    return html_content
+
 @app.teardown_appcontext
 def closeConnection(exception):
     db.close_connection()