Unique file generation API for a given file name

[LRagji]

This API can be used to generate a unique file parameters include
expectFileName: Expected name of the file.
expectedExtension: Expected extension of the file.

Eg:
If expected file name is Laukik.csv thi api will check if this file name exists if it does it will return Laukik0.csv till Laukik'n'.csv else just Laukik.csv

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