xcube v1.7.0 OGC API returns STAC non-conformant collection time extent.

[TejasMorbagal]

Describe the bug

OGC API of xcube server v1.7.0 returns a temporal extent with an invalid format against the STAC Collection spec https://api.stacspec.org/v1.0.0/collections/#tag/Collections/operation/getCollections - the endpoint returns temporal extent as list of lists of lists of strings.

To Reproduce Steps to reproduce the behaviour: Run xcube server v1.7.0 with the following config:

  - Identifier: deep-esdl
    StoreId: s3
    StoreParams:
      root: deep-esdl-public
      storage_options:
        anon: false
    Datasets:
      - Identifier: hydrology
        Path: hydrology-1D-0.009deg-1x1102x966-3.0.2.levels
        Style: default
        Variables:
          - "SM"
          - "*"
        AccessControl:
          # Due to this it will only appear for unauthorized clients
          IsSubstitute: true

Expected behaviour It should be a list of lists of strings

Screenshots

Additional context