accept a function as token

[tusharpandey13]

Allow a sync/async function as token.

Changes

• Modified management client options and management client middleware to accept a function as a token.

Context

This was removed in this commit

Fixes #1050

Tests:

PASSING

Test Suites: 45 passed, 45 total
Tests:       1441 passed, 1441 total
Snapshots:   0 total
Time:        6.842 s, estimated 7 s
Ran all test suites.

Sample:

const managementClient: ManagementClient = new ManagementClient({
    domain: `testdomain`,
    token: async () => 'testtoken',
});