Support required field metadata in data shapes

(Migrated from https://github.com/syndesisio/syndesis/issues/2397)

Author: Zoran Regvart
Assignees: unassigned

This is a...

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[x] Feature request
[ ] Regression (a behavior that used to work and stopped working in a new release)
[ ] Bug report [!-- Please search GitHub for a similar issue or PR before submitting --]
[ ] Documentation issue or request
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The problem

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Currently we don't take into account any metadata of a field in the data shape. Both JSON Schema and XML Stylesheet provide support for setting if property is required, allowed range of the property and similar metadata.
Supporting this would help the user performing the mapping to know what mappings must be performed (required fields), and we could perform mapping validation based on that metadata.

Requires atlasmap/atlasmap#90 atlasmap/atlasmap#50

Expected behavior

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Help the user by highlighting what fields are required and need values mapped to them.