Refactor import blogs action

[jzmalik123]

Changes Made

• Removed transaction block
• Used batch insertion to avoid database connection in each iteration
• insert_all inserts multiple rows into the database in a single SQL statement, which is more efficient than creating each record individually.

Optimization Difference

• Before optimization, the import action took around ~117 seconds to execute csv of 100k records.
  

• After optimization, the import action took around ~6 seconds to execute csv of 100k records.
  

Result

• The optimization made approximately 94% improvement in execution time.

Assumptions

• The data in CSV is already validated and we don't need to handle validations while insertion
• No external gems are allowed in optimisation