Email blocklisting (#718)

* Interface complete for the email blacklisting

* Everything seems to work

* Neutralize language

* fix clippy warnings

* Add missing spaces

* Added matching test

* Correct primary key datatype for postgresql

* Address review comments

* Add placeholder when empty. Fix missing 'i'

migrations/postgres/2020-01-05-232816_add_blocklist/down.sql

@@ -0,0 +1,3 @@
+-- This file should undo anything in `up.sql`
+
+drop table email_blocklist;

migrations/postgres/2020-01-05-232816_add_blocklist/up.sql

@@ -0,0 +1,6 @@
+-- Your SQL goes here
+CREATE TABLE email_blocklist(id SERIAL PRIMARY KEY,
+                             email_address TEXT UNIQUE,
+                             note TEXT,
+                             notify_user BOOLEAN DEFAULT FALSE,
+                             notification_text TEXT);