🤔 [ISSUE] - Refactor processMessage() to Use EnvelopeFactory for Native Blocks

[medchedli]

Description

The current implementation of processMessage() in the BlockService handles the creation of outgoing message envelopes for various block types (text, quick replies, buttons, attachments, content, and plugin-based custom blocks). While the EnvelopeFactory is used in other parts of the service (e.g., processText() and processTokenReplacements()), it is not directly utilized within the main processMessage() logic for native Hexabot blocks. This leads to scattered logic for envelope creation and processing within the function.

This issue proposes an enhancement to refactor the processMessage() logic to leverage the EnvelopeFactory for all block types, including the native ones. This will promote a more consistent and maintainable approach to message envelope generation.