chore(coderd/database): add tasks data model (#19749)

Part of https://github.com/coder/internal/issues/948

Adds the initial part of the tasks data model as per the RFC.

coderd/database/migrations/000366_create_tasks_data_model.up.sql

@@ -0,0 +1,19 @@
+CREATE TABLE tasks (
+	id                  UUID        NOT NULL PRIMARY KEY,
+	organization_id     UUID        NOT NULL REFERENCES organizations     (id) ON DELETE CASCADE,
+	owner_id            UUID        NOT NULL REFERENCES users             (id) ON DELETE CASCADE,
+	name                TEXT        NOT NULL,
+	workspace_id        UUID                 REFERENCES workspaces        (id) ON DELETE CASCADE,
+	template_version_id UUID        NOT NULL REFERENCES template_versions (id) ON DELETE CASCADE,
+	template_parameters JSONB       NOT NULL DEFAULT '{}'::JSONB,
+	prompt              TEXT        NOT NULL,
+	created_at          TIMESTAMPTZ NOT NULL,
+	deleted_at          TIMESTAMPTZ
+);
+
+CREATE TABLE task_workspace_apps (
+	task_id            UUID NOT NULL REFERENCES tasks            (id) ON DELETE CASCADE,
+	workspace_build_id UUID NOT NULL REFERENCES workspace_builds (id) ON DELETE CASCADE,
+	workspace_agent_id UUID NOT NULL REFERENCES workspace_agents (id) ON DELETE CASCADE,
+	workspace_app_id   UUID NOT NULL REFERENCES workspace_apps   (id) ON DELETE CASCADE
+);