discordoauth | PHP implementation of a Discord OAuth2 login flow | REST library

You're trying to assign a foreign key constraint to an integer column, which is not the same as the unsigned columns that Laravel uses for its id's.

In your DiscordOAuths you have to replace $table->integer('id')->unique(); with $table->bigIncrements('id'); or the new method added in Laravel 7 $table->id(); which is an alias of the previous one.

Your discord_id column in the users migration also needs to be an unsigned column. You have to define it using either $table->unsignedBigInteger('discord_id'); or its alias that came with Laravel 7: $table->foreignId('discord_id');

So your migrations would look like this:

For DiscordOAuths