feat(dart): Modify README.md to match our agreed-upon wording (#2503)

1. Change the active development warning to match the Dart standard
warning
2. Replace the existing "Quickstart" section with either nothing (the
default) or customizable text

Author: brianquinlan

internal/sidekick/internal/dart/annotate.go

@@ -54,6 +54,7 @@ type modelAnnotations struct {
 	DoNotPublish         bool
 	RepositoryURL        string
 	ReadMeAfterTitleText string
+	ReadMeQuickstartText string
 }
 
 // HasServices returns true if the model has services.
@@ -223,6 +224,7 @@ func (annotate *annotateModel) annotateModel(options map[string]string) error {
 		devDependencies      = []string{}
 		repositoryURL        string
 		readMeAfterTitleText string
+		readMeQuickstartText string
 	)
 
 	for key, definition := range options {
@@ -250,6 +252,11 @@ func (annotate *annotateModel) annotateModel(options map[string]string) error {
 		case key == "readme-after-title-text":
 			// Markdown that will be inserted into the README.md after the title section.
 			readMeAfterTitleText = definition
+		case key == "readme-quickstart-text":
+			// Markdown that will appear as a "Quickstart" section of README.md. Does not include
+			// the section title, i.e., you probably want it to start with "## Getting Started"`
+			// or similar.
+			readMeQuickstartText = definition
 		case key == "repository-url":
 			repositoryURL = definition
 		case strings.HasPrefix(key, "proto:"):
@@ -337,6 +344,7 @@ func (annotate *annotateModel) annotateModel(options map[string]string) error {
 		DoNotPublish:         doNotPublish,
 		RepositoryURL:        repositoryURL,
 		ReadMeAfterTitleText: readMeAfterTitleText,
+		ReadMeQuickstartText: readMeQuickstartText,
 	}
 
 	model.Codec = ann

internal/sidekick/internal/dart/annotate_test.go

@@ -100,6 +100,15 @@ func TestAnnotateModel_Options(t *testing.T) {
 				}
 			},
 		},
+		{
+			map[string]string{"readme-quickstart-text": "## Getting Started\n..."},
+			func(t *testing.T, am *annotateModel) {
+				codec := model.Codec.(*modelAnnotations)
+				if diff := cmp.Diff("## Getting Started\n...", codec.ReadMeQuickstartText); diff != "" {
+					t.Errorf("mismatch in Codec.ReadMeQuickstartText (-want, +got)\n:%s", diff)
+				}
+			},
+		},
 		{
 			map[string]string{"repository-url": "http://example.com/repo"},
 			func(t *testing.T, am *annotateModel) {

internal/sidekick/internal/dart/templates/README.md.mustache

@@ -19,39 +19,30 @@ The Google Cloud client library for the {{{Title}}}.
 
 <!-- Code generated by sidekick. DO NOT EDIT. -->
 
-> [!CAUTION]
-> This package is under active development! We expect multiple breaking changes
-> in upcoming releases. Testing is also incomplete; we do **not** recommend that
-> you use this package in production.
-
-We welcome feedback about the APIs, documentation, missing features, bugs, etc.
-
 {{#Codec.ReadMeAfterTitleText}}
 {{{Codec.ReadMeAfterTitleText}}}
 
 {{/Codec.ReadMeAfterTitleText}}
+> [!NOTE]
+> This package is currently experimental and published under the
+> [labs.dart.dev](https://dart.dev/dart-team-packages) pub publisher in order
+> to solicit feedback.
+>
+> For packages in the labs.dart.dev publisher we generally plan to either
+> graduate the package into a supported publisher (dart.dev, tools.dart.dev)
+> after a period of feedback and iteration, or discontinue the package.
+> These packages have a much higher expected rate of API and breaking changes.
+>
+> Your feedback is valuable and will help us evolve this package. For general
+> feedback, suggestions, and comments, please file an issue in the
+> [bug tracker]({{Codec.RepositoryURL}}/issues).
+
 ## What's this?
 
 The Google Cloud client library for the {{{Title}}}.
 
 {{Description}}
+{{#Codec.ReadMeQuickstartText}}
 
-## Quickstart
-
-{{#Codec.HasServices}}
-The main clients for this package are:
-
-{{#Services}}
-- `{{Codec.Name}}`
-{{/Services}}
-{{/Codec.HasServices}}
-{{^Codec.HasServices}}
-The main types for this package are:
-
-{{#Messages}}
-- `{{Codec.Name}}`
-{{/Messages}}
-{{#Enums}}
-- `{{Codec.Name}}`
-{{/Enums}}
-{{/Codec.HasServices}}
+{{{Codec.ReadMeQuickstartText}}}
+{{/Codec.ReadMeQuickstartText}}