(core) API reworked to use POST to create webhook and DELET to remove it

Summary:
introduces POST /api/docs/{docId}/webhooks and DELETE /api/docs/{docId}/webhooks/{webhookId} on place of old _subscribe and _unsubscribe endpoints.
Remove checking for unsubscribeKey while deleting webhook - only owner can delete webhook using DELETE endpoint. subscription key is still needed for _unsubscribe endpoint.
old _unsubscribe and _subscribe endpoints are still active and work as before - no changes there.

Posting schema:

```
POST /api/docs/[docId]/webhooks
```

Request Body:

```
{
    "webhooks": [
        {
            "fields": {
                "url": "https://webhook.site/3bd02246-f122-445e-ba7f-bf5ea5bb6eb1",
                "eventTypes": [
                    "add",
                    "update"
                ],
                "enabled": true,
                "name": "WebhookName",
                "memo": "just a text",
                "tableId": "Table1"
            }
        },
        {
            "fields": {
                "url": "https://webhook.site/3bd02246-f122-445e-ba7f-bf5ea5bb6eb2",
                "eventTypes": [
                    "add",
                ],
                "enabled": true,
                "name": "OtherWebhookName",
                "memo": "just a text",
                "tableId": "Table1"
            }
        }
    ]
}
```

Expected response: WebhookId for each webhook posted:

```
{
    "webhooks": [
        {
            "id": "85c77108-f1e1-4217-a50d-acd1c5996da2"
        },
        {
            "id": "d87a6402-cfd7-4822-878c-657308fcc8c3"
        }
    ]
}
```

Deleting webhooks:

```
DELETE api/docs/[docId]/webhooks/[webhookId]
```

there is no payload in DELETE request. Therefore only one webhook can be deleted at once

Response:

```
{
    "success": true
}
```

Test Plan: Old unit test improved to handle new endpoints, and one more added to check if endpoints are in fact created/removed

Reviewers: alexmojaki

Reviewed By: alexmojaki

Subscribers: paulfitz, alexmojaki

Differential Revision: https://phab.getgrist.com/D3916

app/common/Triggers-ti.ts

@@ -14,6 +14,10 @@ export const WebhookFields = t.iface([], {
   "memo": t.opt("string"),
 });
 
+export const Webhook = t.iface([], {
+  "fields": "WebhookFields",
+});
+
 export const WebhookBatchStatus = t.union(t.lit('success'), t.lit('failure'), t.lit('rejected'));
 
 export const WebhookStatus = t.union(t.lit('idle'), t.lit('sending'), t.lit('retrying'), t.lit('postponed'), t.lit('error'), t.lit('invalid'));
@@ -27,6 +31,10 @@ export const WebhookSubscribe = t.iface([], {
   "memo": t.opt("string"),
 });
 
+export const WebhookSubscribeCollection = t.iface([], {
+  "webhooks": t.array("Webhook"),
+});
+
 export const WebhookSummary = t.iface([], {
   "id": "string",
   "fields": t.iface([], {
@@ -80,9 +88,11 @@ export const WebhookUsage = t.iface([], {
 
 const exportedTypeSuite: t.ITypeSuite = {
   WebhookFields,
+  Webhook,
   WebhookBatchStatus,
   WebhookStatus,
   WebhookSubscribe,
+  WebhookSubscribeCollection,
   WebhookSummary,
   WebhookUpdate,
   WebhookPatch,

app/common/Triggers.ts

@@ -1,3 +1,11 @@
+export interface WebhookSubscribeCollection{
+  webhooks: Array<Webhook>
+}
+
+export interface Webhook {
+  fields: WebhookFields;
+}
+
 export interface WebhookFields {
   url: string;
   eventTypes: Array<"add"|"update">;
@@ -24,6 +32,8 @@ export interface WebhookSubscribe {
   memo?: string;
 }
 
+
+
 export interface WebhookSummary {
   id: string;
   fields: {