chore(model): Illustrate defining multiple license fact providers

When multiple providers of the same type are defined, then an `id` has
to be specified explicitly. Illustrate this in `reference.yml`.

Signed-off-by: Frank Viernau <frank.viernau@gmail.com>

Author: fviernau

model/src/main/resources/reference.yml

@@ -38,8 +38,13 @@ ort:
   licenseFactProviders:
   - type: "DefaultDir"
   - type: "Dir"
+    id: "local-custom-license-texts"
     options:
-      licenseTextDir: '/path/to/license/text/dir'
+      licenseTextDir: '/project-sources/.ort/custom-license-texts'
+  - type: "Dir"
+    id: "global-custom-license-texts"
+    options:
+      licenseTextDir: '/ort-config/custom-license-texts'
   - type: "SPDX"
   - type: "ScanCode"
     options:

model/src/test/kotlin/config/OrtConfigurationTest.kt

@@ -63,7 +63,13 @@ class OrtConfigurationTest : WordSpec({
                 ProviderPluginConfiguration(type = "DefaultDir"),
                 ProviderPluginConfiguration(
                     type = "Dir",
-                    options = mapOf("licenseTextDir" to "/path/to/license/text/dir")
+                    id = "local-custom-license-texts",
+                    options = mapOf("licenseTextDir" to "/project-sources/.ort/custom-license-texts")
+                ),
+                ProviderPluginConfiguration(
+                    type = "Dir",
+                    id = "global-custom-license-texts",
+                    options = mapOf("licenseTextDir" to "/ort-config/custom-license-texts")
                 ),
                 ProviderPluginConfiguration(type = "SPDX"),
                 ProviderPluginConfiguration(