Add migration to fix typo
Add support for linking hashtags with posts
Rework tag search page so it says a nicer message than page not found
when no post use that tag
Add new string to translation
we move our PostgreSQL specific migrations to a subdirectory.
The SQLite migrations have been created by running `diesel` against a
copy, and then fixing what's broken.
In the end i reduced all modifications to a single create, since we
*are* starting out fresh with SQLite.
n.b.: i'm not entirely happy with the results yet, because diesel
heavily modifies our `plume-models/src/schema.rs`.
I'll keep fiddling until we have the same types between the two
databases.
