Strapi update username from custom controller - strapi

Question

I am trying to create a custom controller to update the user profile.
I created the routing file and the corresponding controller.
Routing file: server/src/api/profile/routes/profile.js
module.exports = {
routes: [
{
method: 'GET',
path: '/profile',
handler: 'profile.getProfile',
},
{
method: 'PUT',
path: '/profile',
handler: 'profile.updateProfile',
},
]
}
Controller: src/api/profile/controllers/profile.js
async updateProfile(ctx) {
try {
const { id } = ctx.state?.user;
const user = strapi.query('admin::user').update({
where: { id },
data: {
username: "testUsername"
}
})
ctx.body = "User updated"
} catch(error) {
ctx.badRequest("Something went wrong", { error })
}
},
The above code returns "User updated", but the username does not update. I am executing the PUT call with a correct Bearer authorisation token and the user permissions for that user are set to enable "updateProfile".
Oddly enough, the same code, when changed to update a different API item, works perfectly fine:
async updateArticle(ctx) {
try {
const { id } = ctx.state?.user;
const article = strapi.query('api::article.article').update({
where: { author: id },
data: {
title: "New title"
}
})
ctx.body = article
} catch(error) {
ctx.badRequest("Something went wrong", { error })
}
},
I am also confused by different syntaxes appearing in the official Strapi documentation, for example some docs mention:
strapi.query('admin::user').update({ id }, data)
But in other places in the documentation its:
strapi.plugins['users-permissions'].services.user.update({ id });
And then elsewhere:
strapi.query('user', 'users-permissions').update(params, values);
Another question is: do I need to sanitise the input / output in any way? If yes, how? Importing sanitizeEntity from "Strapi-utils" doesn't work, but it's mentioned in several places on the internet.
Additionally, I cannot find a list of all ctx properties. Where can I read what is the difference between ctx.body and ctx.send?
The lack of good documentation is really hindering my development. Any help with this will be greatly appreciated.