0.27.0

What's new:

• core: Fixed error where the main coroutine wasn't awaited if the server failed to start.
• core/ports: Expressions can now be up to 10k characters long.
• lib/templatenotifications: Generalized support for templates for easier subclassing of TemplateNotificationsHandler.
• persist: Added dedicated support for sampling functions.
• persist/postgres: Postgres DB driver now stores samples in a dedicated samples table without JSONB.
• utils/json: Generalizes JSON extra types support (mainly adding ISO format for date & datetime objects).
• Pre-releases version format has been changed from semver to PEP440.

note: Use the following SQL commands to migrate from old Postgres samples format to the new one:

ALTER TABLE value_history RENAME TO value_history_old;
SELECT id::BIGINT, (content->'pid')::TEXT AS oid, (content->'ts')::BIGINT AS ts, CASE WHEN content->'val' = 'false' THEN 0 WHEN content->'val' = 'true' THEN 1 ELSE (content->'val')::double precision END AS val INTO value_history FROM value_history_old;
ALTER TABLE value_history ALTER COLUMN id SET DEFAULT NEXTVAL('value_history_id_seq');
ALTER TABLE value_history ADD PRIMARY KEY (id);
DROP TABLE value_history_old;