feat(server): lossy avatar thumbnails, gzip upload and separate avatar endpoints

contracts/api.schemas.json

@@ -1,6 +1,6 @@
 {
   "$schema": "https://json-schema.org/draft/2020-12/schema",
-  "x-backend-contract-sha256": "a7ea3b6455a14ed68504e9683a38fae13e560bd48df12f3ecf3e82a88f0b83dd",
+  "x-backend-contract-sha256": "96cd0ffa3588a288af7bc720b2413cb56499dd862ac98d83c73ccc11a1147d25",
   "$defs": {
     "AccountChannelBody": {
       "type": "object",
@@ -98,6 +98,9 @@
         "displayName": {
           "type": "string"
         },
+        "hasAvatar": {
+          "type": "boolean"
+        },
         "modifiedAt": {
           "type": "integer"
         },
@@ -107,6 +110,7 @@
       },
       "required": [
         "displayName",
+        "hasAvatar",
         "modifiedAt",
         "username"
       ]
@@ -124,12 +128,26 @@
             }
           ]
         },
+        "avatarThumb": {
+          "anyOf": [
+            {
+              "type": "string"
+            },
+            {
+              "type": "null"
+            }
+          ]
+        },
         "displayName": {
           "type": "string"
+        },
+        "keepAvatar": {
+          "type": "boolean"
         }
       },
       "required": [
-        "displayName"
+        "displayName",
+        "keepAvatar"
       ]
     },
     "AccountRegisterRequest": {
@@ -431,6 +449,16 @@
             }
           ]
         },
+        "avatar_thumb": {
+          "anyOf": [
+            {
+              "type": "string"
+            },
+            {
+              "type": "null"
+            }
+          ]
+        },
         "delete_policy": {
           "anyOf": [
             {