[Persistence] Implement proper SQL migration strategy (i.e. move SQL table schemas to .sql files) about pocket HOT 2 OPEN

Adding to this a comment I put as a review for #73

We can make use of the following tool: dbmate. This tool will basically run in a container alongside the database, and will receive the database URL as an environment variable.

This will allow us to create very simple migrations in SQL, by simply using text directives:

-- migrate:up

-- migrate:down

So an example of a migration would be:

-- migrate:up
create table users (
  id integer,
  name varchar(255),
  email varchar(255) not null
);

-- migrate:down

This migration file will be generated using a command (dbmate new create_users_table) and we will fill it however we see fit.

Then, running the migrations up or down becomes a matter of calling a make command that will send the instruction to the tool in the container, which will subsequently run it against the database, the command would be something like:

migration-up:
	docker exec -v $(PWD)/migrations:/db migrater dbmate up

migration-down:
	docker exec -v $(PWD)/migrations:/db migrater dbmate rollback

And to generate new timestamped migrations:

generate_migration:
   docker exec -v $(PWD)/migrations:/db migrater dbmate new action_table

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@Gustavobelfort Not an immediate priority but this is something we will definitely need and I have a sense you might have some insights on it. It'll cross the boundary of the persistence module implementation and dev tooling

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