feat(ecr): make validateRepositoryName errors human readable (#27186)

When a user specifies an invalid repository name, the error message will now describe why the name is invalid instead of providing the regex used to validate the name. The message comes from the console when defining a new repository. The docstring of `repositoryName` now reflects this and mirrors the docstring of the underlying CFN resource.

Closes #26715.

----

*By submitting this pull request, I confirm that my contribution is made under the terms of the Apache-2.0 license*

packages/aws-cdk-lib/aws-ecr/lib/repository.ts

@@ -493,7 +493,11 @@ export interface OnImageScanCompletedOptions extends events.OnEventOptions {
 
 export interface RepositoryProps {
   /**
-   * Name for this repository
+   * Name for this repository.
+   *
+   * The repository name must start with a letter and can only contain lowercase letters, numbers, hyphens, underscores, and forward slashes.
+   *
+   * > If you specify a name, you cannot perform updates that require replacement of this resource. You can perform updates that require no or some interruption. If you must replace the resource, specify a new name.
    *
    * @default Automatically generated name.
    */
@@ -672,7 +676,7 @@ export class Repository extends RepositoryBase {
     }
     const isPatternMatch = /^(?:[a-z0-9]+(?:[._-][a-z0-9]+)*\/)*[a-z0-9]+(?:[._-][a-z0-9]+)*$/.test(repositoryName);
     if (!isPatternMatch) {
-      errors.push('Repository name must follow the specified pattern: (?:[a-z0-9]+(?:[._-][a-z0-9]+)*/)*[a-z0-9]+(?:[._-][a-z0-9]+)*');
+      errors.push('Repository name must start with a letter and can only contain lowercase letters, numbers, hyphens, underscores, periods and forward slashes');
     }
 
     if (errors.length > 0) {

packages/aws-cdk-lib/aws-ecr/test/repository.test.ts

@@ -898,7 +898,7 @@ describe('repository', () => {
       const expectedErrors = [
         `Invalid ECR repository name (value: ${repositoryName})`,
         'Repository name must be at least 2 and no more than 256 characters',
-        'Repository name must follow the specified pattern: (?:[a-z0-9]+(?:[._-][a-z0-9]+)*/)*[a-z0-9]+(?:[._-][a-z0-9]+)*',
+        'Repository name must start with a letter and can only contain lowercase letters, numbers, hyphens, underscores, periods and forward slashes',
       ].join(EOL);
 
       expect(() => new ecr.Repository(stack, 'Repo', {
@@ -923,19 +923,19 @@ describe('repository', () => {
 
       expect(() => new ecr.Repository(stack, 'Repo1', {
         repositoryName: 'aAa',
-      })).toThrow(/must follow the specified pattern/);
+      })).toThrow('Repository name must start with a letter and can only contain lowercase letters, numbers, hyphens, underscores, periods and forward slashes');
 
       expect(() => new ecr.Repository(stack, 'Repo2', {
         repositoryName: 'a--a',
-      })).toThrow(/must follow the specified pattern/);
+      })).toThrow('Repository name must start with a letter and can only contain lowercase letters, numbers, hyphens, underscores, periods and forward slashes');
 
       expect(() => new ecr.Repository(stack, 'Repo3', {
         repositoryName: 'a./a-a',
-      })).toThrow(/must follow the specified pattern/);
+      })).toThrow('Repository name must start with a letter and can only contain lowercase letters, numbers, hyphens, underscores, periods and forward slashes');
 
       expect(() => new ecr.Repository(stack, 'Repo4', {
         repositoryName: 'a//a-a',
-      })).toThrow(/must follow the specified pattern/);
+      })).toThrow('Repository name must start with a letter and can only contain lowercase letters, numbers, hyphens, underscores, periods and forward slashes');
     });
 
     test('return value addToResourcePolicy', () => {