Add telemetry for CI/CD platform to useragent (#665)

## Changes
This PR adds CI/CD provider infromation to the HTTP user agent. This is
useful to track how often and from which CI/CD platforms our tools are
being run from.
 
## Tests
Unit tests and manually

For manual testing I ran a simple script in Go that list's all jobs in a
workspace and inspected the user agent string.
**Case** **github-actions:**
command: 
```
GITHUB_ACTIONS=true go run main.go
```

User Agent:
```
User-Agent: unknown/0.0.0 databricks-sdk-go/0.23.0 go/1.21.0 os/darwin sdk-feature/pagination auth/pat cicd/github
```

**Case** **google-cloud-build:**
command:
```
PROJECT_ID=1 BUILD_ID=2 PROJECT_NUMBER=3 LOCATION=4  go run main.go
```

User agent:
```
User-Agent: unknown/0.0.0 databricks-sdk-go/0.23.0 go/1.21.0 os/darwin sdk-feature/pagination auth/pat cicd/google-cloud-build
```

client/client.go

@@ -389,6 +389,19 @@ func (c *DatabricksClient) addAuthHeaderToUserAgent(r *http.Request) error {
 	return nil
 }
 
+func (c *DatabricksClient) addCiCdProviderToUserAgent(r *http.Request) error {
+	// Detect if we are running in a CI/CD environment
+	provider := useragent.CiCdProvider()
+	if provider == "" {
+		return nil
+	}
+
+	// Add the detected CI/CD provider to the user agent
+	ctx := useragent.InContext(r.Context(), "cicd", provider)
+	*r = *r.WithContext(ctx) // replace request
+	return nil
+}
+
 func (c *DatabricksClient) perform(
 	ctx context.Context,
 	method,
@@ -407,6 +420,7 @@ func (c *DatabricksClient) perform(
 		c.Config.Authenticate,
 		c.addHostToRequestUrl,
 		c.addAuthHeaderToUserAgent,
+		c.addCiCdProviderToUserAgent,
 	}, visitors...)
 	resp, err := retries.Poll(ctx, c.retryTimeout,
 		c.attempt(ctx, method, requestURL, headers, requestBody, visitors...))

useragent/cicd.go

@@ -0,0 +1,77 @@
+package useragent
+
+import (
+	"os"
+	"sync"
+)
+
+type envVar struct {
+	// Name of the environment variable.
+	name string
+
+	// Expected value of the environment variable. If empty, only the presence
+	// of the environment variable is checked. If non-empty, the value must
+	// match exactly.
+	expectedValue string
+}
+
+type cicdProvider struct {
+	// The name of the CI/CD provider. This is the name included in the user
+	// agent string.
+	name string
+
+	// The env vars that are expected to be set in the CI/CD provider's runner.
+	envVars []envVar
+}
+
+// List of CI/CD providers and their env vars we can rely on to detect them.
+func listCiCdProviders() []cicdProvider {
+	return []cicdProvider{
+		{"github", []envVar{{"GITHUB_ACTIONS", "true"}}},
+		{"gitlab", []envVar{{"GITLAB_CI", "true"}}},
+		{"jenkins", []envVar{{"JENKINS_URL", ""}}},
+		{"azure-devops", []envVar{{"TF_BUILD", "True"}}},
+		{"circle", []envVar{{"CIRCLECI", "true"}}},
+		{"travis", []envVar{{"TRAVIS", "true"}}},
+		{"bitbucket", []envVar{{"BITBUCKET_BUILD_NUMBER", ""}}},
+		{"google-cloud-build", []envVar{{"PROJECT_ID", ""}, {"BUILD_ID", ""}, {"PROJECT_NUMBER", ""}, {"LOCATION", ""}}},
+		{"aws-code-build", []envVar{{"CODEBUILD_BUILD_ARN", ""}}},
+		{"tf-cloud", []envVar{{"TFC_RUN_ID", ""}}},
+	}
+}
+
+// detect returns true if all env vars are set and have expected values.
+func (p cicdProvider) detect() bool {
+	for _, envVar := range p.envVars {
+		v, ok := os.LookupEnv(envVar.name)
+		if !ok {
+			return false
+		}
+		if envVar.expectedValue != "" && v != envVar.expectedValue {
+			return false
+		}
+	}
+	return true
+}
+
+// lookupCiCdProvider returns the name of the CI/CD provider if detected. Returns the
+// first one, if multiple are detected.
+func lookupCiCdProvider() string {
+	for _, p := range listCiCdProviders() {
+		if p.detect() {
+			return p.name
+		}
+	}
+	return ""
+}
+
+var provider string
+
+var providerOnce sync.Once
+
+func CiCdProvider() string {
+	providerOnce.Do(func() {
+		provider = lookupCiCdProvider()
+	})
+	return provider
+}

useragent/cicd_test.go

@@ -0,0 +1,123 @@
+package useragent
+
+import (
+	"testing"
+
+	"github.com/databricks/databricks-sdk-go/internal/env"
+	"github.com/stretchr/testify/assert"
+)
+
+func TestCiCdProviderDetect(t *testing.T) {
+	cicdProvider := cicdProvider{
+		name: "foo",
+		envVars: []envVar{
+			{"APPLE", "123"},
+			{"BANANA", "456"},
+			{"CHERRY", ""},
+		},
+	}
+
+	// Set some of the env vars.
+	t.Setenv("APPLE", "123")
+	t.Setenv("CHERRY", "000")
+	assert.False(t, cicdProvider.detect(), "should not detect when not all env vars are set")
+
+	// Set the rest of the env vars.
+	t.Setenv("BANANA", "456")
+	assert.True(t, cicdProvider.detect(), "should detect when all env vars are set")
+}
+
+func TestCiCdProviderGithubActions(t *testing.T) {
+	env.CleanupEnvironment(t)
+
+	// No provider detected.
+	assert.Equal(t, "", lookupCiCdProvider())
+
+	// Github Actions detected.
+	t.Setenv("GITHUB_ACTIONS", "true")
+	assert.Equal(t, "github", lookupCiCdProvider())
+}
+
+func TestCiCdProviderGitlab(t *testing.T) {
+	env.CleanupEnvironment(t)
+
+	// Gitlab detected.
+	t.Setenv("GITLAB_CI", "true")
+	assert.Equal(t, "gitlab", lookupCiCdProvider())
+}
+
+func TestCiCdProviderJenkins(t *testing.T) {
+	env.CleanupEnvironment(t)
+
+	// Jenkins detected.
+	t.Setenv("JENKINS_URL", "https://jenkins.example.com")
+	assert.Equal(t, "jenkins", lookupCiCdProvider())
+}
+
+func TestCiCdProviderAzureDevops(t *testing.T) {
+	env.CleanupEnvironment(t)
+
+	// Azure Devops detected.
+	t.Setenv("TF_BUILD", "True")
+	assert.Equal(t, "azure-devops", lookupCiCdProvider())
+}
+
+func TestCiCdProviderCircle(t *testing.T) {
+	env.CleanupEnvironment(t)
+
+	// Circle detected.
+	t.Setenv("CIRCLECI", "true")
+	assert.Equal(t, "circle", lookupCiCdProvider())
+}
+
+func TestCiCdProviderTravis(t *testing.T) {
+	env.CleanupEnvironment(t)
+
+	// Travis detected.
+	t.Setenv("TRAVIS", "true")
+	assert.Equal(t, "travis", lookupCiCdProvider())
+}
+
+func TestCiCdProviderBitbucket(t *testing.T) {
+	env.CleanupEnvironment(t)
+
+	// Bitbucket detected.
+	t.Setenv("BITBUCKET_BUILD_NUMBER", "123")
+	assert.Equal(t, "bitbucket", lookupCiCdProvider())
+}
+
+func TestCiCdProviderGoogleCloudBuild(t *testing.T) {
+	env.CleanupEnvironment(t)
+
+	// Google Cloud Build detected.
+	t.Setenv("PROJECT_ID", "foo")
+	t.Setenv("BUILD_ID", "bar")
+	t.Setenv("PROJECT_NUMBER", "baz")
+	t.Setenv("LOCATION", "")
+	assert.Equal(t, "google-cloud-build", lookupCiCdProvider())
+}
+
+func TestCiCdProviderAwsCodeBuild(t *testing.T) {
+	env.CleanupEnvironment(t)
+
+	// AWS Code Build detected.
+	t.Setenv("CODEBUILD_BUILD_ARN", "arn:aws:codebuild:us-east-1:123456789012:build/my-demo-project:b1e6deae-e4f2-4151-be79-3cc4e82a0bf0")
+	assert.Equal(t, "aws-code-build", lookupCiCdProvider())
+}
+
+func TestCiCdProviderTfCloud(t *testing.T) {
+	env.CleanupEnvironment(t)
+
+	// Terraform Cloud detected.
+	t.Setenv("TFC_RUN_ID", "run-123")
+	assert.Equal(t, "tf-cloud", lookupCiCdProvider())
+}
+
+func TestCiCdProviderMultiple(t *testing.T) {
+	env.CleanupEnvironment(t)
+
+	// Multiple providers detected. The first one detected is set.
+	t.Setenv("GITHUB_ACTIONS", "true")
+	t.Setenv("GITLAB_CI", "true")
+	assert.Equal(t, "github", lookupCiCdProvider())
+}