MySQL migration doesn't do Foreign key right

I get the following error:

    Migrating: CREATe TABLE `person_x`( PRIMARY KEY (`username`),`username` TEXT CHARACTER SET utf8 NOT NULL,`name` TEXT CHARACTER SET utf8 NOT NULL,`age` BIGINT NULL)
    CREATe TABLE `person_x`( PRIMARY KEY (`username`),`username` TEXT CHARACTER SET utf8 NOT NULL,`name` TEXT CHARACTER SET utf8 NOT NULL,`age` BIGINT NULL);
    ALTER TABLE `person_x` ADD CONSTRAINT `unique_name` UNIQUE(`name`(200));
    CREATe TABLE `blog_post_x`(`id` BIGINT NOT NULL AUTO_INCREMENT PRIMARY KEY,`title` TEXT CHARACTER SET utf8 NOT NULL,`author_id` TEXT CHARACTER SET utf8 NOT NULL REFERENCES `person_x`);
    ALTER TABLE `blog_post_x` ADD CONSTRAINT `blog_post_x_author_id_fkey` FOREIGN KEY(`author_id`) REFERENCES `person_x`(`username`);
    CREATe TABLE `alias_x`(`id` BIGINT NOT NULL AUTO_INCREMENT PRIMARY KEY,`person` TEXT CHARACTER SET utf8 NOT NULL,`alias` TEXT CHARACTER SET utf8 NOT NULL);
    test: ConnectionError {errFunction = "query", errNumber = 1170, errMessage = "BLOB/TEXT column 'username' used in key specification without a key length"}

from the following migration:

share [mkPersist sqlSettings, mkMigrate "migrateAll", mkDeleteCascade sqlSettings] [persistLowerCase|
PersonX
    username String
    name String
    age Int Maybe
    UniqueName name
    Primary username
    deriving Show
BlogPostX
    title String
    authorId PersonXId
    deriving Show
AliasX
    person String
    alias String
    -- TODO: Uncomment when we can implement non-primary key foreign key
    -- references.
    -- Foreign Person fkperson person name
    deriving Show
|]

Start by reproducing the migration from the issue's PersonX, BlogPostX, and AliasX definitions against MySQL, then inspect the generated CREATE TABLE and ALTER TABLE statements around the author_id foreign key. Done means the migration completes without MySQL error 1170 while preserving the intended foreign-key relationship.