Support scoped access tokens (#20908)

This PR adds the support for scopes of access tokens, mimicking the
design of GitHub OAuth scopes.

The changes of the core logic are in `models/auth` that `AccessToken`
struct will have a `Scope` field. The normalized (no duplication of
scope), comma-separated scope string will be stored in `access_token`
table in the database.
In `services/auth`, the scope will be stored in context, which will be
used by `reqToken` middleware in API calls. Only OAuth2 tokens will have
granular token scopes, while others like BasicAuth will default to scope
`all`.
A large amount of work happens in `routers/api/v1/api.go` and the
corresponding `tests/integration` tests, that is adding necessary scopes
to each of the API calls as they fit.


- [x] Add `Scope` field to `AccessToken`
- [x] Add access control to all API endpoints
- [x] Update frontend & backend for when creating tokens
- [x] Add a database migration for `scope` column (enable 'all' access
to past tokens)

I'm aiming to complete it before Gitea 1.19 release.

Fixes #4300

routers/web/user/setting/applications.go

@@ -42,9 +42,15 @@ func ApplicationsPost(ctx *context.Context) {
 		return
 	}
 
+	scope, err := form.GetScope()
+	if err != nil {
+		ctx.ServerError("GetScope", err)
+		return
+	}
 	t := &auth_model.AccessToken{
-		UID:  ctx.Doer.ID,
-		Name: form.Name,
+		UID:   ctx.Doer.ID,
+		Name:  form.Name,
+		Scope: scope,
 	}
 
 	exist, err := auth_model.AccessTokenByNameExists(t)