MM-17023: Plugin Marketplace (#12183)

* MM-17149 - Extend config.json for marketplace settings (#11933)

* MM-17149 - Extend config.json for marketplace settings

* Renamed MarketplaceUrl, tracking default marketplace url

* Added EnableMarketplace to the client config

* Revert "Added EnableMarketplace to the client config"

This reverts commit 0f982c4c661c2cd9bb96264e9a01a2363c40d9c5.

* MM-17149 - Added EnableMarketplace to the client config (#11958)

* Added EnableMarketplace to the client config

* Moved EnableMarketplace setting out of limited client configuration

* MM-17150, MM-17545, MM-18100 - Implement GET /api/v4/plugins/m… (#11977)

* MM-17150 - Implement GET /api/v4/plugins/marketplace proxying upstream
MM-17545 - Merge locally installed plugins into GET /api/v4/plugins/marketplace

* Replaced MarketplacePluginState with Installed

* Setting InstalledVersion instead of Installed

* marketplace client setting per_page if non zero

* Creating insecure client for marketplace url

* Fixed trailing slash for default marketplace url

* Adding filtering

* Fixed function names

* Renamed Manifest() to GetManifest(), added godoc for BaseMarketplacePlugin

* Handling plugin.ErrNotFound correctly

* Checking err == nil instead when a plugin is installed

* MM-18450 - Local-only plugin search (#12152)

* MM-17846: plugin icons (#12157)

* MM-17846: add support for plugin icons

Extend the model definitions to support plugin icons from the marketplace.

* s/IconURL/IconData

* MM-18475 - Converge on snake_case responses from the marketplace (#12179)

* MM-18520 - MM-Server should forward server version to marketplace server (#12181)

* Renamed request to filter client4.GetMarketplacePlugins

* Renamed request to filter

* Guarding against bad marketplace server response

api4/helpers.go

@@ -0,0 +1,25 @@
+// Copyright (c) 2017-present Mattermost, Inc. All Rights Reserved.
+// See License.txt for license information.
+
+package api4
+
+import (
+	"net/url"
+	"strconv"
+
+	"github.com/pkg/errors"
+)
+
+func parseInt(u *url.URL, name string, defaultValue int) (int, error) {
+	valueStr := u.Query().Get(name)
+	if valueStr == "" {
+		return defaultValue, nil
+	}
+
+	value, err := strconv.Atoi(valueStr)
+	if err != nil {
+		return 0, errors.Wrapf(err, "failed to parse %s as integer", name)
+	}
+
+	return value, nil
+}