feat(tazjin/finito): Check in my old Rust state-machine library

I dug through my archives for this and found a version that, while
unfortunately not the latest implementation, is close enough to the
real thing to show off what Finito did.

This is a Postgres-backed state-machine library for complex
application logic. I wrote this originally for a work purpose in a
previous life, but have always wanted to apply it elsewhere, too.

git-subtree-dir: users/tazjin/finito
git-subtree-mainline: 0380841eb1
git-subtree-split: b748117225
Change-Id: I0de02d6258568447a14870f1a533812a67127763

users/tazjin/finito/finito-postgres/migrations/2018-09-26-160621_bootstrap_finito_schema/down.sql

@@ -0,0 +1,4 @@
+DROP TABLE actions;
+DROP TYPE ActionStatus;
+DROP TABLE events;
+DROP TABLE machines;

users/tazjin/finito/finito-postgres/migrations/2018-09-26-160621_bootstrap_finito_schema/up.sql

@@ -0,0 +1,37 @@
+-- Creates the initial schema required by finito-postgres.
+
+CREATE TABLE machines (
+  id UUID PRIMARY KEY,
+  created TIMESTAMPTZ NOT NULL DEFAULT NOW(),
+  fsm TEXT NOT NULL,
+  state JSONB NOT NULL
+);
+
+CREATE TABLE events (
+  id UUID PRIMARY KEY,
+  created TIMESTAMPTZ NOT NULL DEFAULT NOW(),
+  fsm TEXT NOT NULL,
+  fsm_id UUID NOT NULL REFERENCES machines(id),
+  event JSONB NOT NULL
+);
+CREATE INDEX idx_events_machines ON events(fsm_id);
+
+CREATE TYPE ActionStatus AS ENUM (
+  'Pending',
+  'Completed',
+  'Failed'
+);
+
+CREATE TABLE actions (
+  id UUID PRIMARY KEY,
+  created TIMESTAMPTZ NOT NULL DEFAULT NOW(),
+  fsm TEXT NOT NULL,
+  fsm_id UUID NOT NULL REFERENCES machines(id),
+  event_id UUID NOT NULL REFERENCES events(id),
+  content JSONB NOT NULL,
+  status ActionStatus NOT NULL,
+  error TEXT
+);
+
+CREATE INDEX idx_actions_machines ON actions(fsm_id);
+CREATE INDEX idx_actions_events ON actions(event_id);