merged from gramsrv upstream

deploy/migrations/20260901000008_welcome_message_deliveries.up.sql

@@ -0,0 +1,37 @@
+CREATE SEQUENCE welcome_message_join_event_id_seq AS bigint;
+
+CREATE TABLE welcome_message_deliveries (
+    id bigint GENERATED ALWAYS AS IDENTITY PRIMARY KEY,
+    join_event_id bigint NOT NULL,
+    channel_id bigint NOT NULL REFERENCES channels(id) ON DELETE CASCADE,
+    target_user_id bigint NOT NULL REFERENCES users(id) ON DELETE CASCADE,
+    template_id integer NOT NULL,
+    ephemeral_id integer GENERATED ALWAYS AS (((id - 1) % 2147483646 + 1)::integer) STORED,
+    joined_at integer NOT NULL,
+    content jsonb NOT NULL,
+    attempt_count integer NOT NULL DEFAULT 0,
+    next_attempt_at timestamptz NOT NULL DEFAULT now(),
+    lease_owner text,
+    lease_expires_at timestamptz,
+    delivered_at timestamptz,
+    last_error text NOT NULL DEFAULT '',
+    created_at timestamptz NOT NULL DEFAULT now(),
+    expires_at timestamptz NOT NULL DEFAULT (now() + interval '24 hours'),
+    UNIQUE (join_event_id, template_id),
+    UNIQUE (target_user_id, ephemeral_id),
+    CONSTRAINT welcome_message_deliveries_shape CHECK (
+        join_event_id > 0 AND channel_id > 0 AND target_user_id > 0 AND
+        template_id > 0 AND ephemeral_id > 0 AND joined_at > 0 AND
+        jsonb_typeof(content) = 'object' AND pg_column_size(content) <= 4194304 AND
+        attempt_count >= 0 AND char_length(lease_owner) <= 128 AND
+        char_length(last_error) <= 1024 AND expires_at > created_at AND
+        expires_at <= created_at + interval '24 hours 1 second'
+    )
+);
+
+CREATE INDEX welcome_message_deliveries_due_idx
+    ON welcome_message_deliveries (next_attempt_at, id)
+    WHERE delivered_at IS NULL;
+
+CREATE INDEX welcome_message_deliveries_expiry_idx
+    ON welcome_message_deliveries (expires_at, id);