graphql: Apply authorization on /_search endpoint

- AccessControlContext now resides in a separate package from where it can be imported,
along with the contextKey that will be used to set and retrieve this context value.

- AccessControlContext has a new field called Username, that will be of use for future
implementations in graphQL resolvers.

- GlobalSearch resolver now uses this context to filter repos available to the logged user.

- moved logic for uploading images in tests so that it can be used in every package

- tests were added for multiple request scenarios, when zot-server requires authz
on specific repos

- added tests with injected errors for extended coverage

- added tests for status code error injection utilities

Closes https://github.com/project-zot/zot/issues/615

Signed-off-by: Alex Stan <alexandrustan96@yahoo.ro>

examples/config-tls.json

@@ -8,8 +8,8 @@
     "port": "8080",
     "realm": "zot",
     "tls": {
-      "cert": "test/data/server.cert",
-      "key": "test/data/server.key"
+      "cert": "../../test/data/server.cert",
+      "key": "../../test/data/server.key"
     }
   },
   "log": {