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

tests/integration/migrate_test.go

@@ -11,6 +11,7 @@ import (
 	"path/filepath"
 	"testing"
 
+	auth_model "code.gitea.io/gitea/models/auth"
 	repo_model "code.gitea.io/gitea/models/repo"
 	"code.gitea.io/gitea/models/unittest"
 	user_model "code.gitea.io/gitea/models/user"
@@ -66,7 +67,7 @@ func TestMigrateGiteaForm(t *testing.T) {
 		repoName := "repo1"
 		repoOwner := unittest.AssertExistsAndLoadBean(t, &user_model.User{Name: ownerName})
 		session := loginUser(t, ownerName)
-		token := getTokenForLoggedInUser(t, session)
+		token := getTokenForLoggedInUser(t, session, auth_model.AccessTokenScopeRepo)
 
 		// Step 0: verify the repo is available
 		req := NewRequestf(t, "GET", fmt.Sprintf("/%s/%s", ownerName, repoName))