Added validation for UPI

[nishagraghu]

Added validation for a given UPI so that people can validate the UPI addresses before performing any transaction as per issue #2317 .

Read more about UPI(Unified Payments Interface): https://en.wikipedia.org/wiki/Unified_Payments_Interface

Checklist

• PR contains only changes related; no stray files, etc.
• README updated (where applicable)
• Tests written (where applicable)
• References provided in PR (where applicable)

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 99.95%. Comparing base (b958bd7) to head (3549eb4).
Report is 21 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #2356   +/-   ##
=======================================
  Coverage   99.95%   99.95%           
=======================================
  Files         107      108    +1     
  Lines        2454     2456    +2     
  Branches      619      620    +1     
=======================================
+ Hits         2453     2455    +2     
  Partials        1        1           

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