Change to base62 encoding

[srikrsna]

The current implementation uses an optimised Crockford's base32 encoding (A-Z, 0-9) that is url safe. However due to the limited character set the ids are too long and potentially take up more space. It would be nice if it could be changed to a base64 (url safe) but unfortunately we lose the ability to select a the whole id using a cursor because separation characters like '.'

Hence this should be changed to a base62 notation i.e. (A-Z, a-z, 0-9).

Tasks:

• Add a function to convert []byte to string of base62
• Add a function to parse string in to a []byte

[srikrsna]

@appointy/golang

[imnikhil27]

We can use this library as it also uses timestamp and randomness to generate id and uses base 62 encoding.
https://github.com/segmentio/ksuid

[srikrsna]

Create a Merge request without breaking any tests and API using the new package. If it can work we will use it. Also make sure compare the benchmarks.