[BUG] Validate for existing name when creating detector

[amsiglan]

What is the bug?
When user creates a detector, we are not verifying if a detector with same name already exists.

How can one reproduce the bug?
Steps to reproduce the behavior:

1. Create a detector using create detector API
2. Create another detector with same name

What is the expected behavior?
API fails to created the second detector with error along the lines of detector with same name already exists

What is your host/environment?
NA

Do you have any screenshots?
Na

Do you have any additional context?
NA

[sbcd90]

@raj-chak assigned to you.