Resolve issues with Hierarchical Partition keys

[NikolaPeevski]

I'm submitting a...

[ ] Regression 
[x] Bug report
[ ] Feature request
[ ] Documentation issue or request
[ ] Support request => Please do not submit support request here, instead post your question on Stack Overflow.

Current behavior

Currently, if consumers provide Hierarchical Partition keys (an array of string keys, instead of plain string key) the package errors out, particularly due to the following line of code https://github.com/nestjs/azure-database/blob/master/lib/cosmos-db/cosmos-db.providers.ts#L54
This affects both the package as well as the sample events application

Expected behavior

Support Hierarchical partition keys.

Minimal reproduction of the problem with instructions

1. Clone the repo
2. Configure and ran the sample events project

What is the motivation / use case for changing the behavior?

Environment

Nest version: X.Y.Z

 
For Tooling issues:
- Node version: XX  
- Platform:  

Others:

CC: @kamilmysliwiec @manekinekko