[lib] Make Blob service facts types more strict

Summary:
Part of [[ https://linear.app/comm/issue/ENG-9422/clean-up-blob-service-client-code | ENG-9422 ]] about making types more strict.
Helps to avoid issues like [[ https://linear.app/comm/issue/ENG-9584/removeblobholders-errors-out-when-called-from-delete-accountjs-script#comment-9d0d5abc | ENG-9584 ]].

Test Plan: Flow

Reviewers: ashoat, kamil

Reviewed By: ashoat

Subscribers: tomek

Differential Revision: https://phab.comm.dev/D13696

lib/facts/blob-service.js

@@ -2,16 +2,21 @@
 
 import { isDev } from '../utils/dev-utils.js';
 
-type BlobServicePath = '/blob/:blobHash' | '/blob' | '/holders';
-
-export type BlobServiceHTTPEndpoint = {
-  +path: BlobServicePath,
-  +method: 'GET' | 'POST' | 'PUT' | 'DELETE',
+type BlobHTTPEndpoints = {
+  +GET_BLOB: { +path: '/blob/:blobHash', +method: 'GET' },
+  +ASSIGN_HOLDER: { +path: '/blob', +method: 'POST' },
+  +ASSIGN_MULTIPLE_HOLDERS: { +path: '/holders', +method: 'POST' },
+  +UPLOAD_BLOB: { +path: '/blob', +method: 'PUT' },
+  +DELETE_BLOB: { +path: '/blob', +method: 'DELETE' },
+  +REMOVE_MULTIPLE_HOLDERS: { +path: '/holders', +method: 'DELETE' },
 };
 
+export type BlobServiceHTTPEndpoint =
+  BlobHTTPEndpoints[$Keys<BlobHTTPEndpoints>];
+
 type BlobServiceConfig = {
   +url: string,
-  +httpEndpoints: { +[endpoint: string]: BlobServiceHTTPEndpoint },
+  +httpEndpoints: BlobHTTPEndpoints,
 };
 
 const httpEndpoints = Object.freeze({