[#488] reputation/managers: Implement route builders

Add implementation of Builder interface for
intermediate trusts. Move all code associated
with managers to `common` directory in `cmd`
and `pkg/services/reputation`

Signed-off-by: Pavel Karpy <carpawell@nspcc.ru>

pkg/services/reputation/eigentrust/routes/builder.go

@@ -0,0 +1,52 @@
+package routes
+
+import (
+	"fmt"
+
+	"github.com/nspcc-dev/neofs-node/pkg/services/reputation/common"
+)
+
+// Prm groups the required parameters of the Builder's constructor.
+//
+// All values must comply with the requirements imposed on them.
+// Passing incorrect parameter values will result in constructor
+// failure (error or panic depending on the implementation).
+type Prm struct {
+	// Manager builder for current node.
+	//
+	// Must not be nil.
+	ManagerBuilder common.ManagerBuilder
+}
+
+// Builder represents component that routes node to its managers.
+//
+// For correct operation, Builder must be created using
+// the constructor (New) based on the required parameters
+// and optional components. After successful creation,
+// the Builder is immediately ready to work through API.
+type Builder struct {
+	managerBuilder common.ManagerBuilder
+}
+
+const invalidPrmValFmt = "invalid parameter %s (%T):%v"
+
+func panicOnPrmValue(n string, v interface{}) {
+	panic(fmt.Sprintf(invalidPrmValFmt, n, v, v))
+}
+
+// New creates a new instance of the Builder.
+//
+// Panics if at least one value of the parameters is invalid.
+//
+// The created Builder does not require additional
+// initialization and is completely ready for work.
+func New(prm Prm) *Builder {
+	switch {
+	case prm.ManagerBuilder == nil:
+		panicOnPrmValue("ManagerBuilder", prm.ManagerBuilder)
+	}
+
+	return &Builder{
+		managerBuilder: prm.ManagerBuilder,
+	}
+}