[cds^9.4] feat(node.js): translated error messages (#2087)

delivered with cds 9.4

Co-authored-by: sjvans <[email protected]>

Author: johannes-vogel

node.js/cds-i18n.md

@@ -674,11 +674,11 @@ Ensure you correctly understand how the config option `cds.i18n.folders` work be
 These are the current i18n entries for [`cds.i18n.messages`](#messages) used by the CAP runtime, which you can provide own translations for in your app-specific `_i18n/messages_<locale>.properties` files:
 
 ```properties
-MULTIPLE_ERRORS = Multiple errors occurred. Please see the details for more information.
-ASSERT_FORMAT = Value "{0}" is not in specified format "{1}"
-ASSERT_RANGE = Value {0} is not in specified range [{1}, {2}]
-ASSERT_ENUM = Value {0} is invalid according to enum declaration {{1}}
-ASSERT_NOT_NULL = Value is required
+MULTIPLE_ERRORS = Multiple errors occurred, see details below.
+ASSERT_FORMAT = Enter a value matching the pattern {1}.
+ASSERT_RANGE = Enter a value between {1} and {2}.
+ASSERT_ENUM = Enter one of the allowed values: {1}.
+ASSERT_MANDATORY = Provide the missing value.
 ```
 
 In addition the following HTTP status codes can be translated:

node.js/events.md

@@ -612,3 +612,21 @@ Content-Type: application/json
 > In production, error responses should never disclose internal information that could be exploited by attackers. To ensure that, all errors with a `5xx` status code are returned to the client with only the respective generic message (example: `500 Internal Server Error`).
 >
 > In very rare cases, you might want to return 5xx errors with a meaningful message to the client. This can be achieved with `err.$sanitize = false`. Use that option with care!
+
+
+## Translations for Validation Errors
+
+For the following annotations/error codes, the runtime provides default translations:
+
+| Annotation              | Error Code                      |
+|-------------------------|---------------------------------|
+| `@mandatory`            | ASSERT_MANDATORY<sup>(1)</sup> |
+| `@assert.range`         | ASSERT_RANGE                    |
+| `@assert.range` on enum | ASSERT_ENUM                     |
+| `@assert.format`        | ASSERT_FORMAT                   |
+| `@assert.target`        | ASSERT_TARGET                   |
+
+<sup>(1)</sup> Falls back to error code `ASSERT_NOT_NULL` if provided in custom translations.
+
+These can be overridden by the known technique of providing [custom i18n messages](cds-i18n#localized-messages).
+