Convert Dashboard objects to dict in LakeviewAPI create and update methods

[JCZuurmond]

What changes are proposed in this pull request?

Convert Dashboard objects to dict in LakeviewAPI create and update methods. The API expects a JSON serializable object where the Python dataclasses are not. By converting these dataclass instances to dicts the objects become JSON serializable.

This issue

• Went undetected by the linter as the _api attribute misses type hinting
• Remains for other LakeviewAPI methods
• Breaks the current ucx version
• Breaks the current lsql version

How is this tested?

Did not look into testing this.

[github-actions]

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Trigger:
go/deco-tests-run/sdk-py

Inputs:

• PR number: 824
• Commit SHA: d90db450984b10d36338ebeaf4f80ce3633c50c0

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