improve masking fn

[mixmix]

test and patch masking

[mixmix]

Here's how the testing ran with the old masking function btw:

expected: |-
  { nested: { seed: '*******', secretKey: '***', publicKey: 'data:application/UI8A;base64,BAUG', arr: [ 'a', 'b', 'c' ], obj: { 0: 17, 1: 23 } } }
actual: |-
  { nested: { seed: '*******', secretKey: 'base64:AQID', publicKey: 'base64:BAUG', arr: 'base64:AAAA', obj: 'base64:ERc=' } }

TL;DR - it did not mask ... and it converted some objects/arrays into strings...