update documentation about lambdas (#21241)

docs/templating.md

@@ -820,15 +820,21 @@ Many generators (*those extending DefaultCodegen*) come with a small set of lamb
 
 - `lowercase` - Converts all of the characters in this fragment to lower case using the rules of the `ROOT` locale.
 - `uppercase` - Converts all of the characters in this fragment to upper case using the rules of the `ROOT` locale.
+- `snakecase` - Converts text in a fragment to snake case. For example `once upon a time` to `once_upon_a_time`.
 - `titlecase` - Converts text in a fragment to title case. For example `once upon a time` to `Once Upon A Time`.
+- `kebabcase` - Converts text in a fragment to snake case. For example `Once Upon A Time` to `once-upon-a-time`.
+- `pascalcase` - Converts text in a fragment to snake case. For example `once upon a time` to `OnceUponATime`.
 - `camelcase` - Converts text in a fragment to camelCase. For example `Input-text` to `inputText`.
 - `uncamelize` - Converts text in a fragment from camelCase or PascalCase to a string of words separated by whitespaces. For example `inputText` to `Input Text`.
+- `forwardslash` - Replaces all occurrences of `\/`, `\` and `//` in a fragment by `/`.
+- `backslash` - Replaces all occurrences `/` in a fragment by `\`.
+- `doublequote` - Prepends `"` to the beginning and appends `"` to the end of a fragment.
 - `indented` - Prepends 4 spaces indention from second line of a fragment on. First line will be indented by Mustache.
 - `indented_8` - Prepends 8 spaces indention from second line of a fragment on. First line will be indented by Mustache.
 - `indented_12` - Prepends 12 spaces indention from second line of a fragment on. First line will be indented by Mustache.
 - `indented_16` -Prepends 16 spaces indention from second line of a fragment on. First line will be indented by Mustache.
 
-Lambda is invoked by `lambda.[lambda name]` expression. For example: `{{#lambda.lowercase}}FRAGMENT TO LOWERCASE{{/lambda.lowercase}}` to lower case text between `lambda.lowercase`.
+Some generators provide additional lambdas. Lambda is invoked by `lambda.[lambda name]` expression. For example: `{{#lambda.lowercase}}FRAGMENT TO LOWERCASE{{/lambda.lowercase}}` to lower case text between `lambda.lowercase`.
 
 ## Extensions
 

modules/openapi-generator/src/main/java/org/openapitools/codegen/DefaultCodegen.java

@@ -404,6 +404,8 @@ public class DefaultCodegen implements CodegenConfig {
      * If common lambdas are not desired, override addMustacheLambdas() method
      * and return empty builder.
      *
+     * Corresponding user documentation: docs/templating.md, section "Mustache Lambdas"
+     *
      * @return preinitialized map with common lambdas
      */
     protected ImmutableMap.Builder<String, Lambda> addMustacheLambdas() {