refactor: Proxy and cache avatar images (#907)

* refactor: proxy and cache user avatar images

* fix: extract keys

* fix: set avatar image URL

* fix: show the correct avatar in the list of available users in advanced request

* fix(s): set correct src URL for cached image

* fix: remove unexpired unused image when a user changes their avatar

* fix: requested changes

* refactor: use 'mime' package to detmerine file extension

* style: grammar

* refactor: checks if the default avatar is cached to avoid creating duplicates for different users

* fix: fix vulnerability

* fix: fix incomplete URL substring sanitization

* refactor: only cache avatar with http url protocol

* fix: remove log and correctly set the if statement for the cached image component

* fix: avatar images not showing on issues page

* style: formatting

---------

Co-authored-by: JoaquinOlivero <joaquin.olivero@hotmail.com>

overseerr-api.yml

@@ -2790,6 +2790,15 @@ paths:
                           imageCount:
                             type: number
                             example: 123
+                      avatar:
+                        type: object
+                        properties:
+                          size:
+                            type: number
+                            example: 123456
+                          imageCount:
+                            type: number
+                            example: 123
                   apiCaches:
                     type: array
                     items: