feat: exchange gRPC server implementation to connectRPC (#10145)

# Which Problems Are Solved

The current maintained gRPC server in combination with a REST (grpc)
gateway is getting harder and harder to maintain. Additionally, there
have been and still are issues with supporting / displaying `oneOf`s
correctly.
We therefore decided to exchange the server implementation to
connectRPC, which apart from supporting connect as protocol, also also
"standard" gRCP clients as well as HTTP/1.1 / rest like clients, e.g.
curl directly call the server without any additional gateway.

# How the Problems Are Solved

- All v2 services are moved to connectRPC implementation. (v1 services
are still served as pure grpc servers)
- All gRPC server interceptors were migrated / copied to a corresponding
connectRPC interceptor.
- API.ListGrpcServices and API. ListGrpcMethods were changed to include
the connect services and endpoints.
- gRPC server reflection was changed to a `StaticReflector` using the
`ListGrpcServices` list.
- The `grpc.Server` interfaces was split into different combinations to
be able to handle the different cases (grpc server and prefixed gateway,
connect server with grpc gateway, connect server only, ...)
- Docs of services serving connectRPC only with no additional gateway
(instance, webkey, project, app, org v2 beta) are changed to expose that
- since the plugin is not yet available on buf, we download it using
`postinstall` hook of the docs

# Additional Changes

- WebKey service is added as v2 service (in addition to the current
v2beta)

# Additional Context

closes #9483

---------

Co-authored-by: Elio Bischof <elio@zitadel.com>

internal/api/grpc/user/v2beta/query.go

@@ -3,6 +3,7 @@ package user
 import (
 	"context"
 
+	"connectrpc.com/connect"
 	"github.com/muhlemmer/gu"
 	"google.golang.org/protobuf/types/known/timestamppb"
 
@@ -13,23 +14,23 @@ import (
 	user "github.com/zitadel/zitadel/pkg/grpc/user/v2beta"
 )
 
-func (s *Server) GetUserByID(ctx context.Context, req *user.GetUserByIDRequest) (_ *user.GetUserByIDResponse, err error) {
-	resp, err := s.query.GetUserByIDWithPermission(ctx, true, req.GetUserId(), s.checkPermission)
+func (s *Server) GetUserByID(ctx context.Context, req *connect.Request[user.GetUserByIDRequest]) (_ *connect.Response[user.GetUserByIDResponse], err error) {
+	resp, err := s.query.GetUserByIDWithPermission(ctx, true, req.Msg.GetUserId(), s.checkPermission)
 	if err != nil {
 		return nil, err
 	}
-	return &user.GetUserByIDResponse{
+	return connect.NewResponse(&user.GetUserByIDResponse{
 		Details: object.DomainToDetailsPb(&domain.ObjectDetails{
 			Sequence:      resp.Sequence,
 			EventDate:     resp.ChangeDate,
 			ResourceOwner: resp.ResourceOwner,
 		}),
 		User: userToPb(resp, s.assetAPIPrefix(ctx)),
-	}, nil
+	}), nil
 }
 
-func (s *Server) ListUsers(ctx context.Context, req *user.ListUsersRequest) (*user.ListUsersResponse, error) {
-	queries, err := listUsersRequestToModel(req)
+func (s *Server) ListUsers(ctx context.Context, req *connect.Request[user.ListUsersRequest]) (*connect.Response[user.ListUsersResponse], error) {
+	queries, err := listUsersRequestToModel(req.Msg)
 	if err != nil {
 		return nil, err
 	}
@@ -37,10 +38,10 @@ func (s *Server) ListUsers(ctx context.Context, req *user.ListUsersRequest) (*us
 	if err != nil {
 		return nil, err
 	}
-	return &user.ListUsersResponse{
+	return connect.NewResponse(&user.ListUsersResponse{
 		Result:  UsersToPb(res.Users, s.assetAPIPrefix(ctx)),
 		Details: object.ToListDetails(res.SearchResponse),
-	}, nil
+	}), nil
 }
 
 func UsersToPb(users []*query.User, assetPrefix string) []*user.User {