Port Brave Sync server to Rust

Use SQLite for persistence and generate Rust protobuf bindings at build time.

Add Docker image support for containerized deployment.

Co-Authored-By: codex <[email protected]>

schema/protobuf/sync_pb/entity_metadata.proto

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+// Copyright 2015 The Chromium Authors
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+// If you change or add any fields in this file, update proto_visitors.h and
+// potentially proto_enum_conversions.{h, cc}.
+
+syntax = "proto2";
+
+option go_package = "./sync_pb";
+
+option java_multiple_files = true;
+option java_package = "org.chromium.components.sync.protocol";
+
+option optimize_for = LITE_RUNTIME;
+
+package sync_pb;
+
+import "entity_specifics.proto";
+import "unique_position.proto";
+
+// Sync proto to store entity metadata in model type storage.
+message EntityMetadata {
+  // A hash based on the client tag and model type.
+  // Used for various map lookups. Should always be available.
+  // Sent to the server as SyncEntity::client_tag_hash.
+  optional string client_tag_hash = 1;
+
+  // The entity's server-assigned ID.
+  //
+  // Prior to the item's first commit, we leave this value as an empty string.
+  // The initial ID for a newly created item has to meet certain uniqueness
+  // requirements, and we handle those on the sync thread.
+  optional string server_id = 2;
+
+  // Whether or not the entity is deleted.
+  optional bool is_deleted = 3;
+
+  // A version number used to track in-progress commits. Each local change
+  // increments this number.
+  optional int64 sequence_number = 4;
+
+  // The sequence number of the last item known to be successfully committed.
+  optional int64 acked_sequence_number = 5;
+
+  // The server version on which this item is based.
+  //
+  // If there are no local changes, this is the version of the entity as we see
+  // it here.
+  //
+  // If there are local changes, this is the version of the entity on which
+  // those changes are based.
+  optional int64 server_version = 6 [default = -1];
+
+  // Entity creation and modification timestamps. Assigned by the client and
+  // synced by the server, though the server usually doesn't bother to inspect
+  // their values. They are encoded as milliseconds since the Unix epoch.
+  optional int64 creation_time = 7;
+  optional int64 modification_time = 8;
+
+  // A hash of the current entity specifics value. Used to detect whether
+  // entity's specifics value has changed without having to keep specifics in
+  // memory.
+  optional string specifics_hash = 9;
+
+  // A hash of the last specifics known by both the client and server. Used to
+  // detect when local commits and remote updates are just for encryption. This
+  // value will be the empty string only in the following cases: the entity is
+  // in sync with the server, has never been synced, or is deleted.
+  optional string base_specifics_hash = 10;
+
+  // Used for positioning entities among their siblings. Relevant only for data
+  // types that support positions (e.g bookmarks). Refer to its definition in
+  // unique_position.proto for more information about its internal
+  // representation.
+  optional UniquePosition unique_position = 11;
+
+  // Used only for bookmarks. It's analogous to |specifics_hash| but it
+  // exclusively hashes the content of the favicon image, as represented in
+  // proto field BookmarkSpecifics.favicon, using base::PersistentHash().
+  optional fixed32 bookmark_favicon_hash = 12;
+
+  // Last specifics known by both the client and server. Used during commits to
+  // the server in order to prevent data loss caused by older clients dealing
+  // with unknown proto fields (fields that were introduced later). Datatypes
+  // (ModelTypeSyncBridge) may implement logic to trim down (or fully clear)
+  // this proto prior to caching, to avoid the memory and I/O overhead of
+  // dealing with an extra copy of the data. Introduced in M101.
+  optional EntitySpecifics possibly_trimmed_base_specifics = 13;
+
+  // If the entity is deleted, this field will record the chromium version
+  // (e.g. 117.0.5875.1) that originated the deletion. Introduced in M117.
+  optional string deleted_by_version = 14;
+
+  // Metadata used for shared data types. Must not be present for regular data
+  // types.
+  // Introduced in M124.
+  message CollaborationMetadata {
+    // Collaboration ID which the current entity belongs to.
+    optional string collaboration_id = 1;
+  }
+  optional CollaborationMetadata collaboration = 15;
+}