Implement Postgres interpreter for ConversationStore

[akshaymankar]

https://wearezeta.atlassian.net/browse/WPB-19086

Checklist

• Add a new entry in an appropriate subdirectory of changelog.d
• Read and follow the PR guidelines

[Copilot]

Pull Request Overview

This PR implements a PostgreSQL interpreter for ConversationStore, enabling conversation data to be stored in PostgreSQL instead of Cassandra. The purpose is to provide an alternative data storage backend for conversation-related operations while maintaining compatibility with the existing Cassandra implementation.

Key changes include:

• Implementation of a complete PostgreSQL interpreter for ConversationStore operations
• Addition of new configuration options to control storage location (Cassandra vs PostgreSQL)
• Removal of deprecated Cassandra-only functionality and code cleanup

Reviewed Changes

Copilot reviewed 61 out of 61 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
libs/wire-subsystems/src/Wire/ConversationStore/Postgres.hs	New 1,228-line PostgreSQL interpreter implementation for ConversationStore
services/galley/src/Galley/Options.hs	Added PostgresMigrationOpts configuration and StorageLocation enum
services/galley/src/Galley/App.hs	Integrated PostgreSQL interpreter selection based on configuration
libs/wire-subsystems/src/Wire/ConversationStore.hs	Refactored interface to separate MLSCommitLockStore and update method signatures
Multiple test files	Updated test code to work with the new conversation store interface
Multiple API files	Added PostgreSQL marshalling instances for various data types

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[fisx]

looks nice :-)! hope i didn't leave too many comments. i'm not feeling strongly about most of them.