Fix portal dashboardName validation pattern in metadata (#3568)

There's a mistake in the Azure spec where the max length of a Portal
dashboardName is (correctly) 64, but the regex validation pattern only
allows 24 characters:
Azure/azure-rest-api-specs#30458.

Resolves #3560 

This change corrects the validation regex on our side. After the change:

```
> make local_generate

> cat bin/metadata-compact.json | jq > ../m.json

> rg -A 8 dashboardName ../m.json | rg '(dashboardName|pattern)'
      "path": "/subscriptions/{subscriptionId}/resourceGroups/{resourceGroupName}/providers/Microsoft.Portal/dashboards/{dashboardName}",
          "name": "dashboardName",
      "path": "/subscriptions/{subscriptionId}/resourceGroups/{resourceGroupName}/providers/Microsoft.Portal/dashboards/{dashboardName}",
          "name": "dashboardName",
            "pattern": "^[a-zA-Z0-9-]{3,64}$",
      "path": "/subscriptions/{subscriptionId}/resourceGroups/{resourceGroupName}/providers/Microsoft.Portal/dashboards/{dashboardName}",
          "name": "dashboardName",
            "pattern": "^[a-zA-Z0-9-]{3,64}$",
      "path": "/subscriptions/{subscriptionId}/resourceGroups/{resourceGroupName}/providers/Microsoft.Portal/dashboards/{dashboardName}",
          "name": "dashboardName",
            "pattern": "^[a-zA-Z0-9-]{3,64}$",
      "path": "/subscriptions/{subscriptionId}/resourceGroups/{resourceGroupName}/providers/Microsoft.Portal/dashboards/{dashboardName}",
          "name": "dashboardName",
      "path": "/subscriptions/{subscriptionId}/resourceGroups/{resourceGroupName}/providers/Microsoft.Portal/dashboards/{dashboardName}",
          "name": "dashboardName",
            "pattern": "^[a-zA-Z0-9-]{3,64}$"
      "path": "/subscriptions/{subscriptionId}/resourceGroups/{resourceGroupName}/providers/Microsoft.Portal/dashboards/{dashboardName}",
          "name": "dashboardName",
            "pattern": "^[a-zA-Z0-9-]{3,64}$"
      "path": "/subscriptions/{subscriptionId}/resourceGroups/{resourceGroupName}/providers/Microsoft.Portal/dashboards/{dashboardName}",
          "name": "dashboardName",
            "pattern": "^[a-zA-Z0-9-]{3,64}$"
```

provider/pkg/gen/schema.go

@@ -1308,6 +1308,15 @@ func (m *moduleGenerator) escapeCSharpNames(typeName string, resourceResponse *p
 	}
 }
 
+func normalizeParamPattern(param *openapi.Parameter) string {
+	// #3560: the regex has the wrong max length in the spec.
+	// See portal/resource-manager/Microsoft.Portal/preview/2022-12-01-preview/portal.json#L185-L192
+	if param.Name == "dashboardName" && *param.MaxLength > 24 && param.Pattern == "^[a-zA-Z0-9-]{3,24}$" {
+		return fmt.Sprintf("^[a-zA-Z0-9-]{3,%d}$", *param.MaxLength)
+	}
+	return param.Pattern
+}
+
 func (m *moduleGenerator) genMethodParameters(parameters []spec.Parameter, ctx *openapi.ReferenceContext,
 	namer *resources.AutoNamer, bodySchema *openapi.Schema) (*parameterBag, error) {
 	result := newParameterBag()
@@ -1327,7 +1336,7 @@ func (m *moduleGenerator) genMethodParameters(parameters []spec.Parameter, ctx *
 				Type:      param.Type,
 				MinLength: param.MinLength,
 				MaxLength: param.MaxLength,
-				Pattern:   param.Pattern,
+				Pattern:   normalizeParamPattern(param),
 			},
 		}
 

provider/pkg/gen/schema_test.go

@@ -145,3 +145,55 @@ func TestFindResourcesBodyRefs(t *testing.T) {
 	expected := []string{"#/definitions/Subnet"}
 	assert.Equal(t, expected, actual)
 }
+
+func TestNormalizePattern(t *testing.T) {
+	openapiParam := func(pattern string, maxLength int64) *openapi.Parameter {
+		return &openapi.Parameter{
+			Parameter: &spec.Parameter{
+				CommonValidations: spec.CommonValidations{
+					Pattern:   pattern,
+					MaxLength: &maxLength,
+				},
+				ParamProps: spec.ParamProps{
+					Name: "dashboardName",
+				},
+			},
+		}
+	}
+
+	t.Run("not a dashboard name", func(t *testing.T) {
+		p := openapiParam("^[a-zA-Z0-9-]{3,24}$", 90)
+		p.Name = "foo"
+		assert.Equal(t, "^[a-zA-Z0-9-]{3,24}$", normalizeParamPattern(p))
+	})
+
+	t.Run("empty", func(t *testing.T) {
+		p := openapiParam("", 0)
+		assert.Equal(t, "", normalizeParamPattern(p))
+	})
+
+	t.Run("empty with length", func(t *testing.T) {
+		p := openapiParam("", 90)
+		assert.Equal(t, "", normalizeParamPattern(p))
+	})
+
+	t.Run("pattern without length", func(t *testing.T) {
+		p := openapiParam("^[a-zA-Z0-9-]{3,24}$", 0)
+		assert.Equal(t, "^[a-zA-Z0-9-]{3,24}$", normalizeParamPattern(p))
+	})
+
+	t.Run("pattern with correct length", func(t *testing.T) {
+		p := openapiParam("^[a-zA-Z0-9-]{3,24}$", 24)
+		assert.Equal(t, "^[a-zA-Z0-9-]{3,24}$", normalizeParamPattern(p))
+	})
+
+	t.Run("pattern with shorter length", func(t *testing.T) {
+		p := openapiParam("^[a-zA-Z0-9-]{3,24}$", 23)
+		assert.Equal(t, "^[a-zA-Z0-9-]{3,24}$", normalizeParamPattern(p))
+	})
+
+	t.Run("pattern with longer length", func(t *testing.T) {
+		p := openapiParam("^[a-zA-Z0-9-]{3,24}$", 60)
+		assert.Equal(t, "^[a-zA-Z0-9-]{3,60}$", normalizeParamPattern(p))
+	})
+}