fetchMixDeps: transition to hash

pkgs/applications/audio/sonic-pi/default.nix

···
     pname = "mix-deps-${pname}";
     mixEnv = "test";
     src = "${src}/app/server/beam/tau";
-    sha256 = "sha256-MvwUyVTS23vQKLpGxz46tEVCs/OyYk5dDaBlv+kYg1M=";
+    hash = "sha256-MvwUyVTS23vQKLpGxz46tEVCs/OyYk5dDaBlv+kYg1M=";
   };
 
   strictDeps = true;

pkgs/development/beam-modules/elixir-ls/default.nix

···
   mixFodDeps = fetchMixDeps {
     pname = "mix-deps-${pname}";
     inherit src version elixir;
-    sha256 = "sha256-jF1Plkz1D85aWkiNgeBlJmHndhr7us+8+m/gMkXHvDw=";
+    hash = "sha256-jF1Plkz1D85aWkiNgeBlJmHndhr7us+8+m/gMkXHvDw=";
   };
 
   # elixir-ls is an umbrella app

pkgs/development/beam-modules/fetch-mix-deps.nix

···
 
 { pname
 , version
-, sha256
+, hash ? ""
+, sha256 ? ""
 , src
 , mixEnv ? "prod"
 , debug ? false
···
 , ...
 }@attrs:
 
+let
+  hash_ =
+    if hash != "" then { outputHashAlgo = null; outputHash = hash; }
+    else if sha256 != "" then { outputHashAlgo = "sha256"; outputHash = sha256; }
+    else { outputHashAlgo = "sha256"; outputHash = lib.fakeSha256; };
+in
 stdenvNoCC.mkDerivation (attrs // {
   nativeBuildInputs = [ elixir hex cacert git ];
 
···
     runHook postInstall
   '';
 
-  outputHashAlgo = "sha256";
   outputHashMode = "recursive";
-  outputHash = sha256;
 
   impureEnvVars = lib.fetchers.proxyImpureEnvVars;
   inherit meta;
-})
+} // hash_)

pkgs/servers/web-apps/livebook/default.nix

···
   mixFodDeps = beamPackages.fetchMixDeps {
     pname = "mix-deps-${pname}";
     inherit src version;
-    sha256 = "rwWGs4fGeuyV6BBFgCyyDwKf/YLgs1wY0xnHYy8iioE=";
+    hash = "sha256-rwWGs4fGeuyV6BBFgCyyDwKf/YLgs1wY0xnHYy8iioE=";
   };
 
   installPhase = ''

pkgs/servers/web-apps/plausible/default.nix

···
   mixFodDeps = beamPackages.fetchMixDeps {
     pname = "${pname}-deps";
     inherit src version;
-    sha256 = "1ikcskp4gvvdprl65x1spijdc8dz6klnrnkvgy2jbk0b3d7yn1v5";
+    hash = "sha256-ZQfrTxsLzCWFf3vabOk0vyHWZLw69GJovm3vR+7UbMY=";
   };
 
   yarnDeps = mkYarnModules {