feat: inject secret store csi driver

[omar-devolute]

Description

Fixes #118.

In the deployment_spec.tpl we must allow a new as value to be passed to a secret block, we call this new type "csi".

Receiving this type of secret has to mix functionality of both volumes and environment as we will require a env block and a volumeMounts

Steps

• add template test - to check a csi block is passed to the secret
• modify deployment_spec.tpl so that it can accept "csi" for the values of the "as" and test the template builds appropriately
• add test for csi secret store - that the nginx is built correctly (have to install the helm charts for the secret store)
• find secret related documentation to add details of how this works and how to test it

TODOs

• Update the docs.
• Run the relevant tests successfully, including pre-commit checks.
• Include release notes.

Release Notes (draft)

Allow secrets to be of type CSI allowing the injection of Secret Store CSI driver configuration to the deployment

Migration Guide