debugging: add printing of request & response for schedule override

This is to help with debugging issue #339. This branch is based off of #325, so
that I could make use of the new response debugging functionality I added.

I ran the following commands from within the `command` directory to get the
below result:

```shell
go build -o pd .
./pd schedule override create -authtoken "$(cat ../api.key)" PF4QFIN debug_override.json
```

The `api.key` file is just an API key from the PD console. `PF4QFIN` is a
PagerDuty service in my development account. Here is the output:

```
time="2021-07-04T01:00:24-07:00" level=info msg="service id is:PF4QFIN"
time="2021-07-04T01:00:24-07:00" level=info msg="Input file is:debug_override.json"
req:
req.Method: POST
req.URL: https://api.pagerduty.com/schedules/PF4QFIN/overrides
req.Header: http.Header{"Accept":[]string{"application/vnd.pagerduty+json;version=2"}, "Authorization":[]string{"Token token=u+XP5yPH7pzsQ3aJA5EQ"}, "Content-Type":[]string{"application/json"}, "User-Agent":[]string{"go-pagerduty/1.5.0"}}
req.Body:
{"override":{"start":"2021-06-29T12:00:00Z","end":"2021-06-29T18:00:00Z","user":{"id":"P6QKA9O"}}}

err: HTTP response with status code 400, JSON error object decode failed: json: cannot unmarshal string into Go struct field APIError.error of type []string

resp:
resp.Status: 400 Bad Request
resp.Header: http.Header{"Access-Control-Allow-Headers":[]string{"Authorization, Content-Type, AuthorizationOauth, X-EARLY-ACCESS"}, "Access-Control-Allow-Methods":[]string{"GET, POST, PUT, DELETE, OPTIONS"}, "Access-Control-Allow-Origin":[]string{"*"}, "Access-Control-Expose-Headers":[]string{""}, "Access-Control-Max-Age":[]string{"1728000"}, "Cache-Control":[]string{"no-cache"}, "Connection":[]string{"keep-alive"}, "Content-Length":[]string{"95"}, "Content-Type":[]string{"application/json"}, "Date":[]string{"Sun, 04 Jul 2021 08:00:24 GMT"}, "Server":[]string{"nginx"}, "X-Request-Id":[]string{"f6cda459-587c-49a6-ab98-17fc5bd60642"}}
resp.Body:
{"error":{"message":"Invalid Override","code":2001,"errors":"Invalid input for this override"}}

```

Note that `error.errors` is not an array, it's a single string. This seems to
violate the API spec.

client.go

@@ -401,6 +401,22 @@ func (c *Client) doWithEndpoint(ctx context.Context, endpoint, method, path stri
 
 	c.prepRequest(req, authRequired, headers)
 
+	fmt.Println("req:")
+	fmt.Printf("req.Method: %s\n", req.Method)
+	fmt.Printf("req.URL: %s\n", req.URL.String())
+	fmt.Printf("req.Header: %#v\n", req.Header)
+
+	data, err := ioutil.ReadAll(req.Body)
+	if err != nil {
+		panic(err.Error())
+	}
+
+	req.Body.Close()
+
+	fmt.Printf("req.Body:\n%s\n", string(data))
+
+	req.Body = ioutil.NopCloser(bytes.NewReader(data))
+
 	resp, err := c.HTTPClient.Do(req)
 
 	// debug mode support

command/debug_override.json

@@ -0,0 +1,7 @@
+{
+    "start": "2021-06-29T12:00:00Z",
+    "end": "2021-06-29T18:00:00Z",
+    "user": {
+        "id": "P6QKA9O"
+    }
+}

command/schedule_override_create.go

@@ -3,11 +3,13 @@ package main
 import (
 	"encoding/json"
 	"fmt"
-	"github.com/PagerDuty/go-pagerduty"
-	log "github.com/sirupsen/logrus"
-	"github.com/mitchellh/cli"
+	"io/ioutil"
 	"os"
 	"strings"
+
+	"github.com/PagerDuty/go-pagerduty"
+	"github.com/mitchellh/cli"
+	log "github.com/sirupsen/logrus"
 )
 
 type ScheduleOverrideCreate struct {
@@ -41,14 +43,15 @@ func (c *ScheduleOverrideCreate) Run(args []string) int {
 		return -1
 	}
 	client := c.Meta.Client()
+	client.SetDebugFlag(pagerduty.DebugCaptureLastResponse)
 	var o pagerduty.Override
 	if len(flags.Args()) != 2 {
 		log.Error("Please specify input json file")
 		return -1
 	}
 	log.Info("service id is:", flags.Arg(0))
 	log.Info("Input file is:", flags.Arg(1))
-	f, err := os.Open(flags.Arg(0))
+	f, err := os.Open(flags.Arg(1))
 	if err != nil {
 		log.Error(err)
 		return -1
@@ -62,7 +65,23 @@ func (c *ScheduleOverrideCreate) Run(args []string) int {
 	log.Debugf("%#v", o)
 	o1, err := client.CreateOverride(flags.Arg(0), o)
 	if err != nil {
-		log.Error(err)
+		// log.Error(err)
+
+		fmt.Printf("\n\nerr: %s\n\n", err)
+
+		resp, ok := client.LastAPIResponse()
+		if ok {
+			fmt.Println("resp:")
+			fmt.Printf("resp.Status: %s\n", resp.Status)
+			fmt.Printf("resp.Header: %#v\n", resp.Header)
+
+			body, err := ioutil.ReadAll(resp.Body)
+			if err != nil {
+				panic(err.Error())
+			}
+
+			fmt.Printf("resp.Body:\n%s\n", string(body))
+		}
 		return -1
 	}
 	log.Println("New override id:", o1.ID)