Improved: changed logic of api call for adding mutilple productStores to a facility(#309)

[R-Sourabh]

Related Issues

#309

Short Description and Why It's Useful

• Earlier, all calls were made at the same time (in parallel), which could have caused concurrency issues and the error Transaction is marked for rollback.
• Now, the calls are made one after another (sequentially), which helps avoid these concurrency problems.

Screenshots of Visual Changes before/after (If There Are Any)

Contribution and Currently Important Rules Acceptance

• I read and followed contribution rules