docs: describe each formly extension

src/app/shared/formly/extensions/critical-default-values.extension.ts

@@ -1,5 +1,9 @@
 import { FormlyExtension } from '@ngx-formly/core';
 
+/**
+ * Extension that ensures the validators property is always filled.
+ * This prevents some errors that come with undefined properties.
+ */
 export const criticalDefaultValuesExtension: FormlyExtension = {
   prePopulate(field): void {
     if (field.validators?.validation) {

src/app/shared/formly/extensions/hide-if-empty-options.extension.ts

@@ -2,6 +2,9 @@ import { FormlyExtension } from '@ngx-formly/core';
 import { isObservable, of } from 'rxjs';
 import { map } from 'rxjs/operators';
 
+/**
+ * Extension that automatically hides select fields when their options are empty.
+ */
 export const hideIfEmptyOptionsExtension: FormlyExtension = {
   prePopulate(field): void {
     if (field.type !== 'ish-select-field') {

src/app/shared/formly/extensions/post-wrappers-extension.ts

@@ -1,5 +1,9 @@
 import { FormlyConfig, FormlyExtension, FormlyFieldConfig, FormlyTemplateOptions } from '@ngx-formly/core';
 
+/**
+ * Extension that enables appending wrappers to the default configuration.
+ * It uses the templateOptions.postWrappers to modify a fields wrappers without overriding them.
+ */
 class PostWrappersExtension implements FormlyExtension {
   constructor(private formlyConfig: FormlyConfig) {}
 

src/app/shared/formly/extensions/translate-select-options.extension.ts

@@ -3,6 +3,12 @@ import { TranslateService } from '@ngx-translate/core';
 import { isObservable, of } from 'rxjs';
 import { map, startWith, tap } from 'rxjs/operators';
 
+/**
+ * Extension to translate the templateOptions.options and add a placeholder element.
+ * It will use the TranslateService to translate option labels.
+ * Also, if templateOptions.placeholder is set, the extension will add a placeholder element.
+ * These modified options are written to templateOptions.processedOptions.
+ */
 class TranslateSelectOptionsExtension implements FormlyExtension {
   constructor(private translate: TranslateService) {}