feat: Add Terraform Provider for agent resources (#368)

* ci: Update DataDog GitHub branch to fallback to GITHUB_REF

This was detecting branches, but not our "main" branch before.
Hopefully this fixes it!

* Add basic Terraform Provider

* Rename post files to upload

* Add tests for resources

* Skip instance identity test

* Add tests for ensuring agent get's passed through properly

* Fix linting errors

* Add echo path

* Fix agent authentication

* Update codersdk/files.go

Co-authored-by: Bryan <bryan@coder.com>

Co-authored-by: Bryan <bryan@coder.com>

codersdk/files.go

@@ -3,7 +3,9 @@ package codersdk
 import (
 	"context"
 	"encoding/json"
+	"fmt"
 	"net/http"
+	"net/url"
 
 	"github.com/coder/coder/coderd"
 )
@@ -13,7 +15,7 @@ const (
 )
 
 func (c *Client) UploadFile(ctx context.Context, contentType string, content []byte) (coderd.UploadFileResponse, error) {
-	res, err := c.request(ctx, http.MethodPost, "/api/v2/files", content, func(r *http.Request) {
+	res, err := c.request(ctx, http.MethodPost, "/api/v2/upload", content, func(r *http.Request) {
 		r.Header.Set("Content-Type", contentType)
 	})
 	if err != nil {
@@ -26,3 +28,8 @@ func (c *Client) UploadFile(ctx context.Context, contentType string, content []b
 	var resp coderd.UploadFileResponse
 	return resp, json.NewDecoder(res.Body).Decode(&resp)
 }
+
+// DownloadURL returns the download URL for the specified asset
+func (c *Client) DownloadURL(asset string) (*url.URL, error) {
+	return c.URL.Parse(fmt.Sprintf("/api/v2/downloads/%s", asset))
+}