refactor: move OAuth2 provider code to dedicated package (#18746)

# Refactor OAuth2 Provider Code into Dedicated Package

This PR refactors the OAuth2 provider functionality by moving it from the main `coderd` package into a dedicated `oauth2provider` package. The change improves code organization and maintainability without changing functionality.

Key changes:

- Created a new `oauth2provider` package to house all OAuth2 provider-related code
- Moved existing OAuth2 provider functionality from `coderd/identityprovider` to the new package
- Refactored handler functions to follow a consistent pattern of returning `http.HandlerFunc` instead of being handlers directly
- Split large files into smaller, more focused files organized by functionality:
  - `app_secrets.go` - Manages OAuth2 application secrets
  - `apps.go` - Handles OAuth2 application CRUD operations
  - `authorize.go` - Implements the authorization flow
  - `metadata.go` - Provides OAuth2 metadata endpoints
  - `registration.go` - Handles dynamic client registration
  - `revoke.go` - Implements token revocation
  - `secrets.go` - Manages secret generation and validation
  - `tokens.go` - Handles token issuance and validation

This refactoring improves code organization and makes the OAuth2 provider functionality more maintainable while preserving all existing behavior.

coderd/oauth2provider/revoke.go

@@ -0,0 +1,44 @@
+package oauth2provider
+
+import (
+	"database/sql"
+	"errors"
+	"net/http"
+
+	"github.com/coder/coder/v2/coderd/database"
+	"github.com/coder/coder/v2/coderd/httpapi"
+	"github.com/coder/coder/v2/coderd/httpmw"
+)
+
+func RevokeApp(db database.Store) http.HandlerFunc {
+	return func(rw http.ResponseWriter, r *http.Request) {
+		ctx := r.Context()
+		apiKey := httpmw.APIKey(r)
+		app := httpmw.OAuth2ProviderApp(r)
+
+		err := db.InTx(func(tx database.Store) error {
+			err := tx.DeleteOAuth2ProviderAppCodesByAppAndUserID(ctx, database.DeleteOAuth2ProviderAppCodesByAppAndUserIDParams{
+				AppID:  app.ID,
+				UserID: apiKey.UserID,
+			})
+			if err != nil && !errors.Is(err, sql.ErrNoRows) {
+				return err
+			}
+
+			err = tx.DeleteOAuth2ProviderAppTokensByAppAndUserID(ctx, database.DeleteOAuth2ProviderAppTokensByAppAndUserIDParams{
+				AppID:  app.ID,
+				UserID: apiKey.UserID,
+			})
+			if err != nil && !errors.Is(err, sql.ErrNoRows) {
+				return err
+			}
+
+			return nil
+		}, nil)
+		if err != nil {
+			httpapi.InternalServerError(rw, err)
+			return
+		}
+		rw.WriteHeader(http.StatusNoContent)
+	}
+}