Adds support for PostgreSQL which resolves #87 and is mentioned in #246.

This includes migrations as well as Dockerfile's for amd64.

The biggest change is that replace_into isn't supported by Diesel for the
PostgreSQL backend, instead requiring the use of on_conflict. This
unfortunately requires a branch for save() on all of the models currently
using replace_into.

src/db/models/two_factor.rs

@@ -9,7 +9,7 @@ use crate::error::MapResult;
 
 use super::User;
 
-#[derive(Debug, Identifiable, Queryable, Insertable, Associations)]
+#[derive(Debug, Identifiable, Queryable, Insertable, Associations, AsChangeset)]
 #[table_name = "twofactor"]
 #[belongs_to(User, foreign_key = "user_uuid")]
 #[primary_key(uuid)]
@@ -69,6 +69,18 @@ impl TwoFactor {
 
 /// Database methods
 impl TwoFactor {
+    #[cfg(feature = "postgresql")]
+    pub fn save(&self, conn: &DbConn) -> EmptyResult {
+        diesel::insert_into(twofactor::table)
+            .values(self)
+            .on_conflict(twofactor::uuid)
+            .do_update()
+            .set(self)
+            .execute(&**conn)
+            .map_res("Error saving twofactor")
+    }
+
+    #[cfg(not(feature = "postgresql"))]
     pub fn save(&self, conn: &DbConn) -> EmptyResult {
         diesel::replace_into(twofactor::table)
             .values(self)