fix: Update tags validation message & documentation (#3145)

* Update dns label validation message to match regex pattern

* Update documentation for tags validation & examples

* Add changeset

.changeset/ninety-ads-dance.md

@@ -0,0 +1,5 @@
+---
+'@backstage/catalog-model': patch
+---
+
+Fix documentation and validation message for tags

docs/features/software-catalog/descriptor-format.md

@@ -256,8 +256,8 @@ component, like `java` or `go`.
 
 This field is optional, and currently has no special semantics.
 
-Each tag must be sequences of `[a-zA-Z0-9]` separated by `-`, at most 63
-characters in total.
+Each tag must be sequences of `[a-z0-9]` separated by `-`, at most 63 characters
+in total.
 
 ## Kind: Component
 
@@ -418,7 +418,7 @@ of the `metadata.name` field.
 ### `metadata.tags` [optional]
 
 A list of strings that can be associated with the template, e.g.
-`['Recommended', 'React']`.
+`['recommended', 'react']`.
 
 This list will also be used in the frontend to display to the user so you can
 potentially search and group templates by these tags.

packages/catalog-model/src/entity/policies/FieldFormatEntityPolicy.ts

@@ -74,7 +74,7 @@ export class FieldFormatEntityPolicy implements EntityPolicy {
           case 'isValidNamespace':
           case 'isValidDnsLabel':
             expectation =
-              'a string that is sequences of [a-zA-Z0-9] separated by [-], at most 63 characters in total';
+              'a string that is sequences of [a-z0-9] separated by [-], at most 63 characters in total';
             break;
           case 'isValidAnnotationValue':
             expectation = 'a string';