feat(drs): add SDK support

[pavelnikonorov]

Add SDK support foor the GA4GH Data Repository Service (DRS) API, version 1.4.0.

This issue requires addressing the following steps:

• In the ./lib/src/clients/drs folder, and based on the models added in feat(drs): add models #55, implement a module with client methods for communicating with the DRS API; these include methods for
  • getting an object metadata
  • retrieveing a data object access URL
• Document your code; use the TES client as a template/example
• Provide unit tests for your code; again, use the available TES client as a template/example

Additional context

• This issue is part of meta issue feat(drs): add support for the GA4GH DRS API #54. Refer to it for context and additional information.
• This issue requires feat(drs): add models #55 to be addressed first.