feat: add support for extra containers in deployment configurations

[Dashing-Nelson]

This pull request introduces support for running additional sidecar containers in both the mlflow-tracking-server and oidc-provider-mock Helm charts. The changes allow users to specify extra containers via the extraContainers value in each chart's values.yaml, which are then injected into the respective Kubernetes deployments.

Sidecar container support:

• Added an extraContainers field to charts/mlflow-tracking-server/values.yaml and charts/oidc-provider-mock/values.yaml, including commented examples for user guidance. [1] [2]
• Updated the deployment templates (charts/mlflow-tracking-server/templates/deployment.yaml and charts/oidc-provider-mock/templates/deployment.yaml) to inject any containers defined in extraContainers into the pod spec. [1] [2]

closes #3

[kharkevich]

hi @Dashing-Nelson, could you please update your PR to be in sync with current state of the repo,
also, it will be a really nice if you provide a few use cases when additional container can be useful specific for this helm chart

[Dashing-Nelson]

hi @Dashing-Nelson, could you please update your PR to be in sync with current state of the repo, also, it will be a really nice if you provide a few use cases when additional container can be useful specific for this helm chart

Hello @kharkevich, updated with latest changes from the branch and also added use-cases to the readme file