Fix #1369: Chains Allow Empty Names

[Josh-XT]

Fix #1369: Chains Allow Empty Names

This pull request focuses on adding validation checks to ensure that the chain_name parameter is not empty in various endpoint functions within the agixt/endpoints/Chain.py file. Each affected function now raises an HTTPException with a status code of 400 if the chain_name is empty, improving the robustness and reliability of the code.

Validation improvements:

• Added a check to raise an HTTPException if chain_name is empty in the get_chain function.
• Added a check to raise an HTTPException if chain_name is empty in the run_chain function.
• Added a check to raise an HTTPException if chain_name is empty in the run_chain_step function.
• Added a check to raise an HTTPException if chain_name is empty in the get_chain_args function.
• Added a check to raise an HTTPException if chain_name is empty in the add_chain function.
• Added a check to raise an HTTPException if chain_name is empty in the importchain function.
• Added a check to raise an HTTPException if chain_name is empty in the rename_chain function.
• Added a check to raise an HTTPException if chain_name is empty in the delete_chain function.
• Added a check to raise an HTTPException if chain_name is empty in the add_step function.
• Added a check to raise an HTTPException if chain_name is empty in the update_step function.
• Added a check to raise an HTTPException if chain_name is empty in the move_step function.
• Added a check to raise an HTTPException if chain_name is empty in the delete_step function.