Added securityContext for k8s

[holgerbach]

SecurityContext needed for hardening, which you can define in your values.yaml as follows:

securityContext:
  capabilities:
    drop:
      - ALL
  readOnlyRootFilesystem: true
  allowPrivilegeEscalation: false
  runAsNonRoot: true
  runAsUser: 1000

podSecurityContext:
  readOnlyRootFilesystem: true
  runAsNonRoot: true
  runAsUser: 1000 

• Default
• Version Release

[vincentsarago]

@ividito @ranchodeluxe would you be able to review this PR? 🙏

[ranchodeluxe]

All this looks good @holgerbach thanks for adding those changes 💯 A couple things:

1. can you add securityContext: {} and podSecurityContext: {} as defaults to the values.yml please so this doesn't create empty blocks
2. And please bump the patch number of the chart version https://github.com/developmentseed/titiler/blob/main/deployment/k8s/charts/Chart.yaml#L5 (similar to how this PR did)

[ranchodeluxe]

@holgerbach: I see your previous commit added an empty {} but then you changed your mind.

I don't think most folks will want to use securityContext: by default. Do you mind changing it back to {} as the default?

[ranchodeluxe]

@holgerbach: LGTM now though it seems there's a merge conflict to be resolved around Chart.yml version. Once that's fixed go ahead and merge please.

Note for future us: we'll probably want CI to automatically bump Chart versions for us in the future