Add primary keys to database tables (#1425)

As suggested in #1380, this PR adds Primary keys to the `telescope_entries_tags` and the `telescope_monitoring` tables, to allow HA MySQL deployments.

Co-authored-by: Zois Pagoulatos <[email protected]>

database/migrations/2018_08_08_100000_create_telescope_entries_table.php

@@ -42,7 +42,7 @@ public function up(): void
             $table->uuid('entry_uuid');
             $table->string('tag');
 
-            $table->index(['entry_uuid', 'tag']);
+            $table->primary(['entry_uuid', 'tag']);
             $table->index('tag');
 
             $table->foreign('entry_uuid')
@@ -52,7 +52,7 @@ public function up(): void
         });
 
         $schema->create('telescope_monitoring', function (Blueprint $table) {
-            $table->string('tag');
+            $table->string('tag')->primary();
         });
     }