Add hand-off target upsert (#19)

Closes GRA-430

hand_off_target_upsert.go

@@ -0,0 +1,29 @@
+package client
+
+import (
+	"context"
+	"net/http"
+)
+
+type UpsertHandOffTargetParams struct {
+	// ID is your identifier of choice for this hand-off target. Can be anything consisting
+	// of letters, numbers, or any of the following characters: `_` `-` `+` `=`.
+	ID string `json:"id"`
+
+	// Name is the hand-off target’s name. This cannot be nil.
+	Name string `json:"name"`
+}
+
+// UpsertHandOffTarget inserts or updates a hand-off target
+func (c *Client) UpsertHandOffTarget(ctx context.Context, p *UpsertHandOffTargetParams) error {
+	rsp, err := c.makeRequest(ctx, http.MethodPost, "hand-off-targets", p)
+	if err != nil {
+		return err
+	}
+	defer rsp.Body.Close()
+
+	if err := responseError(rsp); err != nil {
+		return err
+	}
+	return nil
+}

version.go

@@ -1,3 +1,3 @@
 package client
 
-const version = "0.1.1"
+const version = "0.2.0"