chore: Overwrite service webpack configuration

The main change is the addition of :
```
optimization: {
    minimize: false
  }
```
This temporarily patches the problem with the `mjml` package which does not need to be minified, or at least keep the names of these elements to work

app.config.js

@@ -1,5 +1,8 @@
 const merge = require('webpack-merge')
-const config = [require('cozy-scripts/config/webpack.bundle.default.js')]
+const config = [
+  require('cozy-scripts/config/webpack.bundle.default.js'),
+  require('./app.services')
+]
 
 const extraConfig = {
   resolve: {

app.services.js

@@ -0,0 +1,105 @@
+const path = require('path')
+const fs = require('fs')
+const webpack = require('webpack')
+const {
+  target,
+  eslintFix,
+  getFilename
+} = require('cozy-scripts/config/webpack.vars')
+const pathCS = require('cozy-scripts/utils/paths')
+
+const SRC_DIR = path.resolve(__dirname, 'src')
+
+const serviceDir = path.resolve(SRC_DIR, './targets/services/')
+const servicesPaths = fs.existsSync(serviceDir)
+  ? fs.readdirSync(serviceDir)
+  : []
+
+const servicesEntries = {}
+servicesPaths.forEach(file => {
+  if (!file.match(/^[^.]*.js$/)) return
+  const filename = file.match(/^([^.]*).js$/)[1]
+  servicesEntries[filename] = path.resolve(path.join(serviceDir, file))
+})
+
+const config = {
+  __mergeStrategy: {
+    smart: false,
+    strategy: {
+      plugins: 'replace',
+      output: 'replace',
+      entry: 'replace',
+      optimization: 'replace',
+      module: 'replace',
+      externals: 'replace'
+    }
+  },
+  entry: servicesEntries,
+  output: {
+    path: pathCS.appServicesBuild(),
+    filename: `${getFilename(false)}.js`
+  },
+  target: 'node',
+  optimization: {
+    minimize: false
+  },
+  devtool: false,
+  externals: [], // reset externals property
+  module: {
+    rules: [
+      {
+        enforce: 'pre',
+        test: /\.js$/,
+        loader: require.resolve('cozy-scripts/node_modules/eslint-loader'),
+        exclude: /node_modules/,
+        options: {
+          extends: ['cozy-app'],
+          fix: eslintFix,
+          emitWarning: true
+        }
+      },
+      {
+        test: /\.js$/,
+        exclude: /(node_modules|cozy-(bar|client-js))/,
+        loader: require.resolve('cozy-scripts/node_modules/babel-loader'),
+        options: {
+          cacheDirectory: 'cozy-scripts/node_modules/.cache/babel-loader/node',
+          babelrc: false,
+          presets: [['cozy-app', { node: true, react: false }]]
+        }
+      }
+    ],
+    // Dynamic requires produce warnings in webpack. Some of our dependencies
+    // use them for features we do not use, so we can disable them.
+    // More information : https://gitlab.cozycloud.cc/labs/cozy-bank/merge_requests/197#note_4018
+    exprContextRegExp: /$^/,
+    exprContextCritical: false
+  },
+  resolve: {
+    alias: {
+      // We are building with target: node as webpack options. This causes webpack
+      // to consider the "module" entrypoint from node-fetch. This does not work properly
+      // as require('node-fetch') returns a module object (with the default property).
+      // Here, we force the resolution to take the commonJS file.
+      // TODO See if it is necessary to integrate in cozy-scripts
+      'node-fetch': 'node-fetch/lib/index.js',
+      // Unminified Handlebars uses `require.extensions` and this causes
+      // warnings on Webpack. We should think of a way to precompile
+      // our Handlebars template. At the moment it is not possible
+      // since we pass helpers at runtime.
+      handlebars: 'handlebars/dist/handlebars.min.js'
+    }
+  },
+  plugins: [
+    new webpack.DefinePlugin({
+      __TARGET__: JSON.stringify('services')
+    })
+  ]
+}
+
+/* We don't build services if no services and if on mobile build */
+const addServicesConfig =
+  target === 'browser' && Object.keys(servicesEntries).length
+
+// only for browser target (services are usable only on cozy-stack)
+module.exports = addServicesConfig ? { multiple: { services: config } } : {}