Add inventory-item-has-asset-type Constraint

[Gabeblis]

Committer Notes

Purpose

This PR aims to add the inventory-item-has-asset-type constraint which ensures that each inventory item, or it's linked component, has the "asset-type" prop.

Changes

Added constraint:

• inventory-item-has-asset-type

Added invalid test content:

• ssp-inventory-item-has-is-scanned-INVALID.xml

Added yaml files for testing:

• Pass/fail yaml tests added for each of the above constraints.

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By submitting a pull request, you are agreeing to provide this contribution under the CC0 1.0 Universal public domain dedication.

[Rene2mt]

Looks good!! Will need a rebase before merging though.

[wandmagic]

@Rene2mt merged in latest changes from develop, needs another review