Add a table to immutably store the verified email of the version publisher

The publisher's email address is deliberatel copied into this table rather
than referencing the users table. If people delete their account, remove
their email, etc we still have a way to attempt to contact the publisher
of a particular version in the event of a DMCA complaint.

Author: carols10cents

migrations/2019-02-12-200540_track_version_published_by_email/down.sql

@@ -0,0 +1 @@
+DROP TABLE versions_published_by;

migrations/2019-02-12-200540_track_version_published_by_email/up.sql

@@ -0,0 +1,4 @@
+CREATE TABLE versions_published_by (
+    version_id INTEGER NOT NULL PRIMARY KEY REFERENCES versions(id) ON DELETE CASCADE,
+    email VARCHAR NOT NULL
+);

src/schema.rs

@@ -912,6 +912,30 @@ table! {
     }
 }
 
+table! {
+    use diesel::sql_types::*;
+    use diesel_full_text_search::{TsVector as Tsvector};
+    use diesel_ltree::Ltree;
+
+    /// Representation of the `versions_published_by` table.
+    ///
+    /// (Automatically generated by Diesel.)
+    versions_published_by (version_id) {
+        /// The `version_id` column of the `versions_published_by` table.
+        ///
+        /// Its SQL type is `Int4`.
+        ///
+        /// (Automatically generated by Diesel.)
+        version_id -> Int4,
+        /// The `email` column of the `versions_published_by` table.
+        ///
+        /// Its SQL type is `Varchar`.
+        ///
+        /// (Automatically generated by Diesel.)
+        email -> Varchar,
+    }
+}
+
 joinable!(api_tokens -> users (user_id));
 joinable!(crate_downloads -> crates (crate_id));
 joinable!(crate_owner_invitations -> crates (crate_id));
@@ -934,6 +958,7 @@ joinable!(version_authors -> versions (version_id));
 joinable!(version_downloads -> versions (version_id));
 joinable!(versions -> crates (crate_id));
 joinable!(versions -> users (published_by));
+joinable!(versions_published_by -> versions (version_id));
 
 allow_tables_to_appear_in_same_query!(
     api_tokens,
@@ -958,4 +983,5 @@ allow_tables_to_appear_in_same_query!(
     version_authors,
     version_downloads,
     versions,
+    versions_published_by,
 );