fix: Make CompositeSchedule (2.0.1) type to comply with the schema

[sderkacs]

Proposed changes

• Fix CompositeSchedule type (and associated ChargingSchedulePeriod) to comply with OCPP 2.0.1 schema
• Update the relevant tests

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• New feature (non-breaking change which adds functionality)
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Checklist

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Further comments

This fix is related to the issue #385.