fix: add a mock router to avoid panic in the coordinator client process

[agneum]

Fixed panic:

panic: runtime error: invalid memory address or nil pointer dereference
spqr-coordinator-1  | [signal SIGSEGV: segmentation violation code=0x1 addr=0x30 pc=0x8cd99e]
spqr-coordinator-1  | 
spqr-coordinator-1  | goroutine 67 [running]:
spqr-coordinator-1  | github.com/pg-sharding/spqr/router/pkg/route.(*Route).Params(0x0)
spqr-coordinator-1  | 	/home/go/src/github.com/pg-sharding/spqr/router/pkg/route/route.go:59 +0x5e
spqr-coordinator-1  | github.com/pg-sharding/spqr/router/pkg/client.(*PsqlClient).Auth(0xc0005b8db8, 0xda0f26?)
spqr-coordinator-1  | 	/home/go/src/github.com/pg-sharding/spqr/router/pkg/client/client.go:511 +0x30a
spqr-coordinator-1  | github.com/pg-sharding/spqr/coordinator/provider.(*qdbCoordinator).ProcClient(0xc00007e140?, {0xeb1430, 0xc000038040}, {0xeb3d70, 0xc0003a0000})
spqr-coordinator-1  | 	/home/go/src/github.com/pg-sharding/spqr/coordinator/provider/coordinator.go:351 +0x306
spqr-coordinator-1  | github.com/pg-sharding/spqr/coordinator/app.(*App).ServePsql(0xc000592020, 0x0?)
spqr-coordinator-1  | 	/home/go/src/github.com/pg-sharding/spqr/coordinator/app/app.go:63 +0x1ea
spqr-coordinator-1  | github.com/pg-sharding/spqr/coordinator/app.(*App).Run.func2(0x0?)
spqr-coordinator-1  | 	/home/go/src/github.com/pg-sharding/spqr/coordinator/app/app.go:40 +0x35
spqr-coordinator-1  | created by github.com/pg-sharding/spqr/coordinator/app.(*App).Run
spqr-coordinator-1  | 	/home/go/src/github.com/pg-sharding/spqr/coordinator/app/app.go:39 +0x18d