Various improvements and bug fixes for Event Sourcing Samples

[oskardudycz]

1. Made an alignment of ECommerce samples: ECommerce samples alignment #118:

• Renamed Initialize Shopping Cart to Open Shopping Cart to be more closer to real terminology,
• Added Cancel Shopping Cart operation,
• Aligned Product Items implementation.

2. Updated MartenEventPublisher to publish events with metadata Updated MartenEventPublisher to publish events with metadata.  #112
3. Fixed Marten Append Scope registration: Fixed Marten Append Scope registration #111
4. Upgraded Marten to v5 release candidate 1: Upgraded Marten to v5 release candidate 1 #115
5. Shift tenant to aggregateId part of streamId to properly handle EventStoreDB category projections: Shift tenant to aggregateId part of streamId to properly handle EventStoreDB category projections #117

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This discussion was created from the release Various improvements and bug fixes for Event Sourcing Samples.