docs: add a migrations_and_tasks guide

documentation/migrations_and_tasks.md

@@ -1,9 +1,24 @@
 # Migrations
 
+## Tasks
+
+The available tasks are:
+
+* `mix ash_postgres.create`
+* `mix ash_postgres.drop`
+* `mix ash_postgres.migrate` (use `mix ash_postgres.migrate --tenants` to run tenant migrations)
+
 AshPostgres is built on top of ecto, so much of its behavior is pass-through/orchestration of that tooling.
 
-For instance, you can use `mix ash_postgres.generate_migrations` to generate a snapshot and a migration to take
-your resources from the previous version to this version. For more information, see the module documentation here:
+## Basic Workflow
+
+* Make resource changes
+* Run `mix ash_postgres.generate_migrations` to generate migrations and resource snapshots
+* Run `mix ash_postgres.migrate` to run those migrations
+* Run `mix ash_postgres.migrate --tenants` *as well* if you have multi-tenant resources.
+
+
+For more information on generating migrations, see the module documentation here:
 `Mix.Tasks.AshPostgres.GenerateMigrations`, or run `mix help ash_postgres.generate_migrations`
 
 For running your migrations, there is a mix task that will find all of the repos configured in your apis and run their
@@ -16,4 +31,5 @@ For tenant migrations (see the multitenancy guides for more) generated by multit
 
 ## Multiple Repos
 
-If you are using multiple repos, you will likely need to use `mix ecto.migrate` and manage it separately for each repo.
+If you are using multiple repos, you will likely need to use `mix ecto.migrate` and manage it separately for each repo, as the options would
+be applied to both repo, which wouldn't make sense.

mix.exs

@@ -53,6 +53,7 @@ defmodule AshPostgres.MixProject do
       logo: "logos/small-logo.png",
       extras: [
         "README.md",
+        "documentation/migrations_and_tasks.md",
         "documentation/multitenancy.md"
       ],
       groups_for_extras: [