Added the ability to get tags from the database.

Also fixed the way the example was compiling so it didn't act weird on
other features.

tavern/src/database.rs

@@ -274,6 +274,27 @@ impl Database
       Ok(())
    }
 
+   #[cfg(any(not(feature = "publisher"), feature = "tester"))]
+   pub async fn get_all_tags(&self) -> Result<Vec<String>>
+   {
+      let mut tx = self.pool.begin().await?;
+
+      let rows = sqlx::query!(
+          "SELECT name FROM tags ORDER BY name ASC"
+      )
+      .fetch_all(&mut *tx)
+      .await?;
+
+      tx.commit().await?;
+
+      let tags = rows
+         .into_iter()
+         .filter_map(|row| Some(row.name))
+         .collect();
+
+      Ok(tags)
+   }
+
    #[cfg(any(not(feature = "publisher"), feature = "tester"))]
    pub async fn get_tales_summary(&self, categories: &[String])
                                   -> Result<Vec<Lore>>