Add random string generation capabilities

[yorinasub17]

In the GCP bootstrap script I am currently developing, I have a need to generate a random string that I can use as a unique identifier for seeding the Project ID when creating a new project. I haven't seen us provide this as a library outside of terratest, so I ported a version of random.UniqueId here that is more generic, where you can control char sets and digits.

Note that this uses crypto/rand instead of math/rand, to allow for potential usage with password generation.

[brikis98]

Neat 👍

[brikis98]

Oh wait, I think with all the special characters, this is not base 62. At the least, the variable should be renamed. Note also that the special characters may limit reusability of this unique ID, as many identifiers and even passwords don't allow those characters, whereas almost everything supports alphanumeric.

[yorinasub17]

This doesn't have the special characters 😉

[brikis98]

Oh... Right. So is that variable unused?

[yorinasub17]

This is a convenience variable. The function allows you to control what characters to use to generate the string. Examples:

// Only lower case chars + digits
random.RandomString(6, random.Digits + random.LowerLetters)

// alphanumerics + special chars
random.RandomString(6, random.Base62Chars + random.SpecialChars)

// Only alphanumerics (base62)
random.RandomString(6, random.Base62Chars)

// Only abc
random.RandomString(6, "abc")

[brikis98]

Ohhh, I gotcha now. Perhaps add a test case using some of the other character sets to make that a bit clearer?

[yorinasub17]

Addressed in d9def43

[yorinasub17]

Ok addressed the question about being more clear about the usage. Will merge now and release. Thanks for the review!