Refactor Mailbox Schema

[pheller]

• cache list of message ids in session on client entry to mailbox (when mailbox page 1 is retrieved)
• client message indexes are offsets into this cached list
• if client leaves and comes back to mailbox, client requests page 1 again, refreshing the cache

[Copilot]

Pull Request Overview

This PR refactors the mailbox schema to address session-based message indexing. The key change is moving from database-stored sequential indexes to session-cached message IDs, allowing client message indexes to be offsets into a cached list that refreshes when entering the mailbox.

• Replaces composite primary key (to_id, index) with auto-incrementing id field in messages
• Implements session-based message ID caching that loads on mailbox page 1 requests
• Updates message operations to use client indices as offsets into the cached message ID list

Reviewed Changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
apps/server/lib/prodigy/server/session.ex	Adds messaging field to session struct for caching message IDs
apps/server/lib/prodigy/server/service/messaging.ex	Core refactor implementing session-based indexing and message ID caching
apps/core/lib/prodigy/core/data/message.ex	Removes composite primary key and index field from Message schema
apps/core/priv/repo/migrations/20250907183440_fix_message_ids.exs	Database migration to replace composite key with auto-incrementing id
apps/server/test/prodigy/server/service/messaging_test.exs	Updates tests to reflect new client indexing behavior and verify correct message operations

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[Copilot]

Pull Request Overview

Copilot reviewed 5 out of 5 changed files in this pull request and generated 1 comment.

Comments suppressed due to low confidence (2)

apps/server/lib/prodigy/server/service/messaging.ex:1

• The pattern match _ -> catches all non-{:ok, payload} responses including errors, but always returns {:ok, session}. This could mask actual errors. Consider explicitly handling :ok responses and error cases separately.

# Copyright 2022, Phillip Heller

apps/server/lib/prodigy/server/service/messaging.ex:344

• The unhandled case returns {:ok, <<0>>} but should return {session, {:ok, <<0>>}} to match the expected tuple format used throughout the function.

          Logger.warn(
            "unhandled messaging request: #{inspect(request, base: :hex, limit: :infinity)}"
          )

          {:ok, <<0>>}

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