Tweak appearance of invite reason

This adjusts the display of invite reasons to match design feedback.

Fixes https://github.com/vector-im/element-web/issues/16869

src/components/views/elements/InviteReason.tsx

@@ -0,0 +1,62 @@
+/*
+Copyright 2021 The Matrix.org Foundation C.I.C.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+import classNames from "classnames";
+import React from "react";
+import { _t } from "../../../languageHandler";
+import { replaceableComponent } from "../../../utils/replaceableComponent";
+
+interface IProps {
+    reason: string;
+}
+
+interface IState {
+    hidden: boolean;
+}
+
+@replaceableComponent("views.elements.InviteReason")
+export default class InviteReason extends React.PureComponent<IProps, IState> {
+    constructor(props) {
+        super(props);
+        this.state = {
+            // We hide the reason for invitation by default, since it can be a
+            // vector for spam/harassment.
+            hidden: true,
+        };
+    }
+
+    onToggleClick = () => {
+        this.setState({
+            hidden: false,
+        });
+    }
+
+    render() {
+        const classes = classNames({
+            "mx_InviteReason": true,
+            "mx_InviteReason_hidden": this.state.hidden,
+        });
+
+        return <div className={classes}>
+            <div className="mx_InviteReason_reason">{this.props.reason}</div>
+            <div className="mx_InviteReason_toggle"
+                onClick={this.onToggleClick}
+            >
+                {_t("View message")}
+            </div>
+        </div>;
+    }
+}