Mono repo -> Master (#22553)

Combines the following repositories into one:

https://github.com/mattermost/mattermost-server
https://github.com/mattermost/mattermost-webapp
https://github.com/mattermost/focalboard
https://github.com/mattermost/mattermost-plugin-playbooks

server/platform/shared/filestore/s3_overrides.go

@@ -0,0 +1,55 @@
+// Copyright (c) 2015-present Mattermost, Inc. All Rights Reserved.
+// See LICENSE.txt for license information.
+
+package filestore
+
+import (
+	"context"
+	"net/http"
+
+	"github.com/minio/minio-go/v7/pkg/credentials"
+)
+
+// customTransport is used to point the request to a different server.
+// This is helpful in situations where a different service is handling AWS S3 requests
+// from multiple Mattermost applications, and the Mattermost service itself does not
+// have any S3 credentials.
+type customTransport struct {
+	host   string
+	scheme string
+	client http.Client
+}
+
+// RoundTrip implements the http.Roundtripper interface.
+func (t *customTransport) RoundTrip(req *http.Request) (*http.Response, error) {
+	// Roundtrippers should not modify the original request.
+	newReq := req.Clone(context.Background())
+	*newReq.URL = *req.URL
+	req.URL.Scheme = t.scheme
+	req.URL.Host = t.host
+	return t.client.Do(req)
+}
+
+// customProvider is a dummy credentials provider for the minio client to work
+// without actually providing credentials. This is needed with a custom transport
+// in cases where the minio client does not actually have credentials with itself,
+// rather needs responses from another entity.
+//
+// It satisfies the credentials.Provider interface.
+type customProvider struct {
+	isSignV2 bool
+}
+
+// Retrieve just returns empty credentials.
+func (cp customProvider) Retrieve() (credentials.Value, error) {
+	sign := credentials.SignatureV4
+	if cp.isSignV2 {
+		sign = credentials.SignatureV2
+	}
+	return credentials.Value{
+		SignerType: sign,
+	}, nil
+}
+
+// IsExpired always returns false.
+func (cp customProvider) IsExpired() bool { return false }