Test implementation of Kubernetes with a Vitess cluster

[frouioui]

Small prototype and test of a Kubernetes cluster implementation using a Vitess MySQL database cluster (https://vitess.io).

This prototype focuses on the user table implementation. The goal is to be able to shard the user table accordingly to the region attribute:

• Beijing will go in shard '-80'
• Hong Kong will go in shard '80-'

[frouioui]

This commit contains a decent version of the prototype. The README.md file contains the list of all the commands that we need to run to get the cluster fully setup.

This version, so far, allow creating a Vitess cluster, create the user table, create a sequence for the auto incrementation of the _id column in a namespace config, creation of Lookup Vindex and region_vdx for region-based sharding, and finally: the sharding in 2 equal parts of the user namespace, with repartition based on the region attribute.

[frouioui]

Merging this PR, the next research direction could be the implementation of other tables (such as article, etc...), and their keyspaces implementation in the cluster, the monitoring with prometheus, backup system, etc... Issues and PR will be created for the latter maters.