[BUG] Remove default values for created_at and modified_at from the database

[dracarys18]

Context

Currently we are setting created_at and modified_at in the database during insert through Posgresql now() function which gives the current time according to the current time zone. But when we modify the data we pass common_utils::date_time::now to update modified at which gives the date time in UTC.

Resolution

Remove default values for created_at and modified_at from database and add it in DatabaseStructNew struct. Which forces the developer to pass these values while inserting, which fixes inconsistencies of these two values between database and application