Upgrade bootstrapping of initial accounts, added body to provisioning request

Description:

ADR: #110 (closed)

/tenant-provisioning was upgraded to consume the request body, the endpoint method did not change since it already was a POST method.

The body is a list of alias mappings, it does not allow directly giving permissions to accounts, all alias mappings configurations should be provided in CSP resources:

{
  "aliasMappings": [
    {
      "aliasId": "ALIAS_ID",
      "userId": "my.account@email.com"
    },
    {
      "aliasId": "ANY_OTHER_ALIAS_ID",
      "userId": "other.account.@email.com"
    }
  ]
}

Changes include:

• Refactor (a non-breaking change that improves code maintainability).
• Bugfix (a non-breaking change that solves an issue).
• New feature (a non-breaking change that adds functionality).
• Breaking change (a change that is not backward-compatible and/or changes current functionality).

Changes in:

• Common code