Upgrade project to use ESM imports

[kdhttps]

Currently, we are using commonjs format where we add libs in a project using require('module') but some libs(e.g. got) are stoping this and moving on to the latest javascript technique that is ESM(ECMA Script Module) which use import and export syntax for use lib. CommonJS does not allow to use/import of ESM Modules but the ESM technique allows both ESM and CommonJS so it is good to upgrade projects to use ESM.

discussion #401 (comment)

[kdhttps]

@christian-hawk mate, rewire is not supporting ESM https://github.com/jhnns/rewire#limitations. There is one package babel-plugin-rewire but it depends on babel which means we have to rebuild/restructure whole gluu-passport. There is not any other package for this so I guess we have to modify our code and test cases. Please share your thoughts