Add integration testing with OpenSearch

[dblock]

Is your feature request related to a problem? Please describe.

In a conversation here we said that security plugin relies on unit tests. Given how tightly coupled security is with many other plugins we may want to bring in some integration testing into the project and cover any dependencies.

Describe the solution you'd like

Integration testing run as part of CI.

[peternied]

Thanks @dblock closing this issue in favor of #1761