fix: sync support private chat content protection

deploy/migrations/0159_private_no_forwards.down.sql

@@ -0,0 +1,2 @@
+DROP TABLE IF EXISTS private_no_forwards_requests;
+DROP TABLE IF EXISTS private_no_forwards_chats;

deploy/migrations/0159_private_no_forwards.up.sql

@@ -0,0 +1,36 @@
+CREATE TABLE private_no_forwards_chats (
+    user_low_id bigint NOT NULL REFERENCES users(id) ON DELETE CASCADE,
+    user_high_id bigint NOT NULL REFERENCES users(id) ON DELETE CASCADE,
+    enabled_by_user_id bigint REFERENCES users(id) ON DELETE CASCADE,
+    created_at timestamptz NOT NULL DEFAULT now(),
+    updated_at timestamptz NOT NULL DEFAULT now(),
+    PRIMARY KEY (user_low_id, user_high_id),
+    CONSTRAINT private_no_forwards_distinct_users CHECK (user_low_id < user_high_id),
+    CONSTRAINT private_no_forwards_enabled_participant CHECK (
+        enabled_by_user_id IS NULL
+        OR enabled_by_user_id = user_low_id
+        OR enabled_by_user_id = user_high_id
+    )
+);
+
+CREATE TABLE private_no_forwards_requests (
+    private_message_sender_user_id bigint NOT NULL,
+    private_message_id bigint NOT NULL,
+    requester_user_id bigint NOT NULL REFERENCES users(id) ON DELETE CASCADE,
+    responder_user_id bigint NOT NULL REFERENCES users(id) ON DELETE CASCADE,
+    expires_at integer NOT NULL,
+    handled_at integer NOT NULL DEFAULT 0,
+    created_at timestamptz NOT NULL DEFAULT now(),
+    PRIMARY KEY (private_message_sender_user_id, private_message_id),
+    CONSTRAINT private_no_forwards_request_message_fk
+        FOREIGN KEY (private_message_sender_user_id, private_message_id)
+        REFERENCES private_messages(sender_user_id, id) ON DELETE CASCADE,
+    CONSTRAINT private_no_forwards_request_distinct_users
+        CHECK (requester_user_id <> responder_user_id),
+    CONSTRAINT private_no_forwards_request_valid_expiry
+        CHECK (expires_at > 0 AND handled_at >= 0)
+);
+
+CREATE INDEX private_no_forwards_requests_responder_expiry_idx
+    ON private_no_forwards_requests (responder_user_id, expires_at)
+    WHERE handled_at = 0;