Validate dataset and namespace

[ruflin]

dataset and namespace can only have a length of 100 chars and certain chars cannot be used. This should be validated. See elastic/kibana#75846 for more details.

[jsoriano]

@ruflin @jen-huang not sure what should be validated from the spec regarding these values. I also wonder if something is needed, as the changes mentioned in the original issue seem to be in the configuration Fleet UI.

There are different things that could apply to this, but not sure about the scope:

In package-spec:

• dataset setting in data stream manifest doesn't have any validation now, and it seems to be barely used, but we could check the length there.
• type in data stream is already limited to certain values (metrics, logs, synthetics and traces)
• There is no setting for namespace.

In elastic-package we could check the values of certain fields during testing, but which ones?

• data_stream.type?
• data_stream.dataset?
• data_stream.namespace?

Are they actually related to what is checked in elastic/kibana#75381?

[ruflin]

• The data_stream.* fields are the ones that should be validate if these exist with a value in fields.yml.
• As in most cases the directory name defines the dataset value, the directory name should be validated (likely already the case)
• If the dataset field is used in the manifest.yml, it should be validate

Ideally it is also ensured, that the values in the fields and manifest are aligned and cannot contradict it each.

As you mentioned, namespace is not set at all on the package level and I currently can't think of a reason why it should so I would leave this to Kibana.