feat(AIP-203): introduce IDENTIFIER field behavior (#1201)

Identifier fields are often multi-modal: they are required or optional
in various situations. Adding an explicit field behavior for these
fields helps eliminate ambiguity for an author to fully annotate field
behavior on all request fields, as well as clarify which fields to use
in identifying the resource for clients.

Author: toumorokoshi

aip/client-libraries/4231.md

@@ -43,10 +43,7 @@ message Topic {
     pattern: "projects/{project}/topics/{topic}"
   };
 
-  // The resource's name.
-  string name = 1;
-
-  // And so on...
+  // name and so on...
 }
 ```
 
@@ -91,10 +88,7 @@ message LogEntry {
     pattern: "billingAccounts/{billing_account}/logs/{log}"
   };
 
-  // The resource's name.
-  string name = 1;
-
-  // And so on...
+  // name and so on...
 }
 ```
 
@@ -195,10 +189,7 @@ message FeedItemTarget {
     pattern: "customers/{customer}/feedItemTargets/{feed}~{feed_item}"
   };
 
-  // The resource name of this event.
-  string name = 1;
-
-  // Other fields...
+  // name and other fields...
 }
 ```
 

aip/cloud/2510.md

@@ -88,7 +88,7 @@ message Book {
   };
 
   // The resource name of the Book.
-  string name = 1;
+  string name = 1 [(google.api.field_behavior) = IDENTIFIER];
 
   // A reference to another resource, a Shelf.
   string shelf = 2 [(google.api.resource_reference) = {

aip/general/0122.md

@@ -196,7 +196,7 @@ message Book {
 
   // The resource name of the book.
   // Format: publishers/{publisher}/books/{book}
-  string name = 1;
+  string name = 1 [(google.api.field_behavior) = IDENTIFIER];
 
   // Other fields...
 }
@@ -282,7 +282,7 @@ When a field represents another resource, the field **should** be of type
 `string` and accept the resource name of the other resource. The field name
 **should** be equivalent to the corresponding message's name in snake case.
 
-The field **should not** be of type `message` using the `message` that 
+The field **should not** be of type `message` using the `message` that
 implements the resource, _unless_ the API is internal-only, has tight lifecycle
 relationships, and has a permission model that enables inherited access to
 embedded resources.
@@ -307,7 +307,7 @@ message Book {
 
   // Name of the book.
   // Format is `publishers/{publisher}/books/{book}`
-  string name = 1;
+  string name = 1 [(google.api.field_behavior) = IDENTIFIER];
 
   // The shelf where the book currently sits.
   // Format is `shelves/{shelf}`.

aip/general/0123.md

@@ -67,10 +67,7 @@ message Topic {
     plural: "topics"
   };
 
-  // The resource name of the topic.
-  string name = 1;
-
-  // Other fields...
+  // Name and other fields...
 }
 ```
 

aip/general/0124.md

@@ -36,7 +36,7 @@ message Book {
   };
 
   // The resource name for the book.
-  string name = 1;
+  string name = 1 [(google.api.field_behavior) = IDENTIFIER];
 
   // The resource name for the book's author.
   string author = 2 [(google.api.resource_reference) = {
@@ -71,7 +71,7 @@ message Book {
     pattern: "publishers/{publisher}/books/{book}"
   };
 
-  string name = 1;
+  string name = 1 [(google.api.field_behavior) = IDENTIFIER];
 
   // The resource names for the book's authors.
   repeated string authors = 2 [(google.api.resource_reference) = {
@@ -97,7 +97,7 @@ message BookAuthor {
   };
 
   // The resource name for the book-author association.
-  string name = 1;
+  string name = 1 [(google.api.field_behavior) = IDENTIFIER];
 
   // The resource name for the author.
   string author = 2 [(google.api.resource_reference) = {

aip/general/0128.md

@@ -44,8 +44,7 @@ message Book {
     style: DECLARATIVE_FRIENDLY
   };
 
-  string name = 1;
-  // Other fields...
+  // Name and other fields...
 }
 ```
 

aip/general/0134.md

@@ -227,9 +227,14 @@ In this situation, the resource **should** contain a `string etag` field:
 
 ```proto
 message Book {
+  option (google.api.resource) = {
+    type: "library.googleapis.com/Book"
+    pattern: "publishers/{publisher}/books/{book}"
+  };
+
   // The resource name of the book.
   // Format: publishers/{publisher}/books/{book}
-  string name = 1;
+  string name = 1 [(google.api.field_behavior) = IDENTIFIER];
 
   // The title of the book.
   // Example: "Mary Poppins"

aip/general/0144.md

@@ -20,7 +20,13 @@ Resources **may** use repeated fields where appropriate.
 
 ```proto
 message Book {
-  string name = 1;
+  option (google.api.resource) = {
+    type: "library.googleapis.com/Book"
+    pattern: "publishers/{publisher}/books/{book}"
+  };
+
+  string name = 1 [(google.api.field_behavior) = IDENTIFIER];
+
   repeated string authors = 2;
 }
 ```

aip/general/0147.md

@@ -25,7 +25,7 @@ resource implies storage of the sensitive data. For example:
 
 ```proto
 message SelfManagedKeypair {
-  string name = 1;
+  string name = 1 [(google.api.field_behavior) = IDENTIFIER];
 
   // The public key data in PEM-encoded form.
   bytes public_key = 2;
@@ -42,7 +42,7 @@ indicate whether or not the sensitive information is present. For example:
 
 ```proto
 message Integration {
-  string name = 1;
+  string name = 1 [(google.api.field_behavior) = IDENTIFIER];
   string uri = 2;
 
   // A secret to be passed in the `Authorization` header of the webhook.

aip/general/0149.md

@@ -25,8 +25,13 @@ its default value (`0`, `false`, or empty string) from not setting it at all:
 ```proto
 // A representation of a book in a library.
 message Book {
+  option (google.api.resource) = {
+    type: "library.googleapis.com/Book"
+    pattern: "publishers/{publisher}/books/{book}"
+  };
+
   // The name of the book.
-  string name = 1;
+  string name = 1 [(google.api.field_behavior) = IDENTIFIER];
 
   // The rating for the book, from 0 to 5.
   // 0 is distinct from no rating.