merged from gramsrv upstream

deploy/migrations/20260901000007_welcome_messages.up.sql

@@ -0,0 +1,31 @@
+CREATE TABLE welcome_message_peers (
+    channel_id bigint PRIMARY KEY REFERENCES channels(id) ON DELETE CASCADE,
+    next_id integer NOT NULL DEFAULT 1,
+    revision bigint NOT NULL DEFAULT 1,
+    updated_at timestamptz NOT NULL DEFAULT now(),
+    CONSTRAINT welcome_message_peers_shape CHECK (
+        channel_id > 0 AND next_id > 0 AND next_id <= 2147483647 AND revision > 0
+    )
+);
+
+CREATE TABLE welcome_messages (
+    channel_id bigint NOT NULL REFERENCES welcome_message_peers(channel_id) ON DELETE CASCADE,
+    id integer NOT NULL,
+    creator_user_id bigint NOT NULL REFERENCES users(id) ON DELETE RESTRICT,
+    date integer NOT NULL,
+    edit_date integer NOT NULL DEFAULT 0,
+    random_id bigint NOT NULL,
+    content jsonb NOT NULL,
+    create_fingerprint bytea NOT NULL,
+    version bigint NOT NULL DEFAULT 1,
+    created_at timestamptz NOT NULL DEFAULT now(),
+    updated_at timestamptz NOT NULL DEFAULT now(),
+    PRIMARY KEY (channel_id, id),
+    UNIQUE (channel_id, creator_user_id, random_id),
+    CONSTRAINT welcome_messages_shape CHECK (
+        channel_id > 0 AND id > 0 AND creator_user_id > 0 AND date > 0 AND
+        edit_date >= 0 AND (edit_date = 0 OR edit_date >= date) AND random_id <> 0 AND
+        jsonb_typeof(content) = 'object' AND pg_column_size(content) <= 4194304 AND
+        octet_length(create_fingerprint) = 32 AND version > 0
+    )
+);