Fix validation messages after Shoelace update

- some messages (textbox) were out of position
- Selectboxes did not show validation message
- Selectbox considered false a valid value for required, even if that wasn't an option

api/js/etemplate/Et2InputWidget/Et2InputWidget.ts

@@ -7,6 +7,9 @@ import {LionValidationFeedback, Validator} from "@lion/form-core";
 import {et2_csvSplit} from "../et2_core_common";
 import {dedupeMixin} from "@lion/core";
 
+// LionValidationFeedback needs to be registered manually
+window.customElements.define('lion-validation-feedback', LionValidationFeedback);
+
 /**
  * This mixin will allow any LitElement to become an Et2InputWidget
  *
@@ -87,7 +90,7 @@ const Et2InputWidgetMixin = <T extends Constructor<LitElement>>(superclass : T)
 					width: 100%;
 				  }
 
-				  .form-field__feedback {
+				  .form-control__help-text {
 					position: relative;
 				  }
 				`

api/js/etemplate/Et2Select/Et2Select.ts

@@ -327,7 +327,7 @@ export class Et2Select extends Et2WithSearchMixin(Et2WidgetWithSelect)
 		}
 
 		// emptyLabel is fine
-		if(!(this.value) && this.value !== '0' && (this.emptyLabel || this.placeholder))
+		if((this.value == '' || this.value == []) && (this.emptyLabel || this.placeholder))
 		{
 			return;
 		}
@@ -856,6 +856,9 @@ export class Et2Select extends Et2WithSearchMixin(Et2WidgetWithSelect)
                 ${this._optionsTemplate()}
                 ${this._extraTemplate()}
                 <slot></slot>
+                <div slot="help-text">
+                    <slot name="feedback"></slot>
+                </div>
             </sl-select>
 		`;
 	}

api/templates/default/etemplate2.css

@@ -2130,6 +2130,8 @@ div.message.floating, lion-validation-feedback[type] {
 lion-validation-feedback[type] {
     top: initial;
     margin-top: calc(-0.2 * var(--sl-input-height-medium));
+	width: fit-content;
+	white-space: nowrap;
 }
 
 .message.validation_error, lion-validation-feedback[type="error"] {