Add toLower() and `toUpper() function

Author: Gijsreyn

docs/reference/schemas/config/functions/toLower.md

@@ -0,0 +1,219 @@
+---
+description: Reference for the 'toLower' DSC configuration document function
+ms.date:     10/03/2025
+ms.topic:    reference
+title:       toLower
+---
+
+# toLower
+
+## Synopsis
+
+Converts the specified string to lower case.
+
+## Syntax
+
+```Syntax
+toLower(<stringToChange>)
+```
+
+## Description
+
+The `toLower()` function converts all uppercase letters in the input string to
+lowercase letters. Numbers, symbols, punctuation, and whitespace are unchanged.
+The function supports Unicode characters and preserves the original string
+structure. Use it for normalizing string comparisons, creating consistent
+naming conventions, or formatting output for case-sensitive operations.
+
+## Examples
+
+### Example 1 - Normalize resource names
+
+The following example converts a parameter value to lowercase for consistent
+resource naming.
+
+```yaml
+# tolower.example.1.dsc.config.yaml
+$schema: https://aka.ms/dsc/schemas/v3/bundled/config/document.json
+parameters:
+  resourceName:
+    type: string
+    defaultValue: WEB-API-SERVICE
+resources:
+- name: Resource name normalization
+  type: Microsoft.DSC.Debug/Echo
+  properties:
+    output:
+      originalName: "[parameters('resourceName')]"
+      normalizedName: "[toLower(parameters('resourceName'))]"
+```
+
+```bash
+dsc config get --file tolower.example.1.dsc.config.yaml
+```
+
+```yaml
+results:
+- name: Resource name normalization
+  type: Microsoft.DSC.Debug/Echo
+  result:
+    actualState:
+      output:
+        originalName: WEB-API-SERVICE
+        normalizedName: web-api-service
+messages: []
+hadErrors: false
+```
+
+### Example 2 - Create consistent file paths
+
+The following example demonstrates using `toLower()` with the [`concat()`][01]
+function to create lowercase file paths.
+
+```yaml
+# tolower.example.2.dsc.config.yaml
+$schema: https://aka.ms/dsc/schemas/v3/bundled/config/document.json
+parameters:
+  fileName:
+    type: string
+    defaultValue: CONFIG-FILE
+  extension:
+    type: string
+    defaultValue: JSON
+resources:
+- name: File path creation
+  type: Microsoft.DSC.Debug/Echo
+  properties:
+    output:
+      filePath: "[concat('/etc/', toLower(parameters('fileName')), '.', toLower(parameters('extension')))]"
+```
+
+```bash
+dsc config get --file tolower.example.2.dsc.config.yaml
+```
+
+```yaml
+results:
+- name: File path creation
+  type: Microsoft.DSC.Debug/Echo
+  result:
+    actualState:
+      output:
+        filePath: /etc/config-file.json
+messages: []
+hadErrors: false
+```
+
+### Example 3 - Case-insensitive comparison preparation
+
+The following example uses `toLower()` to normalize strings for comparison
+using the `equals()` function.
+
+```yaml
+# tolower.example.3.dsc.config.yaml
+$schema: https://aka.ms/dsc/schemas/v3/bundled/config/document.json
+parameters:
+  userInput:
+    type: string
+    defaultValue: Production
+  expectedValue:
+    type: string
+    defaultValue: PRODUCTION
+resources:
+- name: Case-insensitive comparison
+  type: Microsoft.DSC.Debug/Echo
+  properties:
+    output:
+      matches: "[equals(toLower(parameters('userInput')), toLower(parameters('expectedValue')))]"
+```
+
+```bash
+dsc config get --file tolower.example.3.dsc.config.yaml
+```
+
+```yaml
+results:
+- name: Case-insensitive comparison
+  type: Microsoft.DSC.Debug/Echo
+  result:
+    actualState:
+      output:
+        matches: true
+messages: []
+hadErrors: false
+```
+
+### Example 4 - Unicode and special character handling
+
+The following example shows how `toLower()` handles Unicode characters and
+preserves special characters.
+
+```yaml
+# tolower.example.4.dsc.config.yaml
+$schema: https://aka.ms/dsc/schemas/v3/bundled/config/document.json
+resources:
+- name: Unicode and special character conversion
+  type: Microsoft.DSC.Debug/Echo
+  properties:
+    output:
+      ascii: "[toLower('HELLO WORLD!')]"
+      unicode: "[toLower('CAFÉ RÉSUMÉ')]"
+      mixed: "[toLower('SERVER-01 (PRIMARY)')]"
+```
+
+```bash
+dsc config get --file tolower.example.4.dsc.config.yaml
+```
+
+```yaml
+results:
+- name: Unicode and special character conversion
+  type: Microsoft.DSC.Debug/Echo
+  result:
+    actualState:
+      output:
+        ascii: hello world!
+        unicode: café résumé
+        mixed: server-01 (primary)
+messages: []
+hadErrors: false
+```
+
+## Parameters
+
+### stringToChange
+
+The string value to convert to lower case.
+
+```yaml
+Type:     string
+Required: true
+Position: 1
+```
+
+## Output
+
+The `toLower()` function returns the input string with all uppercase letters
+converted to lowercase. Numbers, symbols, punctuation, and whitespace remain
+unchanged.
+
+```yaml
+Type: string
+```
+
+## Related functions
+
+- [`toUpper()`][00] - Converts a string to upper case
+- [`concat()`][01] - Concatenates strings together
+- [`equals()`][02] - Compares two values for equality
+- [`if()`][03] - Returns values based on a condition
+- [`string()`][04] - Converts values to strings
+- [`parameters()`][05] - Retrieves parameter values
+
+<!-- Link reference definitions -->
+[00]: ./toUpper.md
+[01]: ./concat.md
+[02]: ./equals.md
+[03]: ./if.md
+[04]: ./string.md
+[05]: ./parameters.md