software/theia: download extensions using slapos.recipe.build 's download

slapos.recipe.build verifies signatures of downloaded files and can also use
buildout cache or download from shacache, which

This introduces a new download-plugins.cfg, containing the URLs of
extensions and their md5sum signatures. This profile is extended by
software.cfg and there's a section using slapos.recipe.build to actually
download extensions.

A generate_download_plugins_cfg.py python script is also included, to be
run by software release maintainers to update download-plugins.cfg using the
list of plugins included in generate_download_plugins_cfg.py

software/theia/generate_download_plugins_cfg.py

+import configparser
+import requests
+import hashlib
+
+urls = []
+
+for plugin_and_version in '''\
+    vscode/bat/1.44.2
+    vscode/clojure/1.44.2
+    vscode/coffeescript/1.44.2
+    vscode/configuration-editing/1.44.2
+    vscode/cpp/1.44.2
+    vscode/csharp/1.44.2
+    vscode/css/1.44.2
+    vscode/css-language-features/1.45.1
+    vscode/debug-auto-launch/1.44.2
+    vscode/docker/1.44.2
+    vscode/emmet/1.44.2
+    vscode/fsharp/1.44.2
+    vscode/go/1.44.2
+    vscode/groovy/1.44.2
+    vscode/grunt/1.44.2
+    vscode/gulp/1.44.2
+    vscode/handlebars/1.44.2
+    vscode/hlsl/1.44.2
+    vscode/html/1.48.0-next.4a1bcdafe9
+    vscode/html-language-features/1.48.0-next.4a1bcdafe9
+    vscode/ini/1.44.2
+    vscode/jake/1.44.2
+    vscode/java/1.44.2
+    vscode/javascript/1.44.2
+    ms-vscode/js-debug/1.49.8
+    vscode/json/1.46.1
+    vscode/json-language-features/1.46.1
+    vscode/less/1.44.2
+    vscode/log/1.44.2
+    vscode/lua/1.44.2
+    vscode/make/1.44.2
+    vscode/markdown/1.44.2
+    vscode/markdown-language-features/1.39.1
+    vscode/merge-conflict/1.44.2
+    vscode/npm/1.44.2
+    ms-vscode/node-debug/1.44.8
+    ms-vscode/node-debug2/1.42.1
+    vscode/objective-c/1.44.2
+    vscode/perl/1.44.2
+    vscode/powershell/1.44.2
+    vscode/pug/1.44.2
+    vscode/python/1.44.2
+    vscode/r/1.44.2
+    vscode/razor/1.44.2
+    vscode/ruby/1.44.2
+    vscode/rust/1.44.2
+    vscode/scss/1.44.2
+    vscode/shaderlab/1.44.2
+    vscode/shellscript/1.44.2
+    vscode/sql/1.44.2
+    vscode/swift/1.44.2
+    vscode/theme-abyss/1.44.2
+    vscode/theme-defaults/1.44.2
+    vscode/theme-kimbie-dark/1.44.2
+    vscode/theme-monokai/1.44.2
+    vscode/theme-monokai-dimmed/1.44.2
+    vscode/theme-quietlight/1.44.2
+    vscode/theme-red/1.44.2
+    vscode/theme-solarized-dark/1.44.2
+    vscode/theme-tomorrow-night-blue/1.44.2
+    vscode/typescript/1.44.2
+    vscode/typescript-language-features/1.44.2
+    vscode/vb/1.44.2
+    vscode/vscode-theme-seti/1.44.2
+    vscode/xml/1.44.2
+    vscode/yaml/1.44.2
+    EditorConfig/EditorConfig/0.14.4
+    dbaeumer/vscode-eslint/2.1.1
+    ms-vscode/references-view/0.0.47
+    golang/Go/0.16.2
+    vscjava/vscode-java-debug/0.29.0
+    redhat/java/0.61.0
+    vscjava/vscode-java-test/0.26.0
+    ms-python/python/2020.9.112786
+    perrinjerome/vscode-zc-buildout/0.4.0
+    jebbs/plantuml/2.13.12
+    rafaelmaiolla/diff/0.0.1
+    perrinjerome/git-commit-syntax/0.0.1
+    perrinjerome/git-rebase-syntax/0.0.1
+'''.splitlines():
+  plugin_and_version = plugin_and_version.strip()
+  if not plugin_and_version or plugin_and_version.startswith('#'):
+    continue
+  publisher, extension_name, version = plugin_and_version.split('/')
+
+  api_url = f'https://open-vsx.org/api/{publisher}/{extension_name}/{version}'
+  download_url = requests.get(api_url).json()['files']['download']
+  md5sum = hashlib.md5(requests.get(download_url).content).hexdigest()
+  urls.append(f'{publisher}-{extension_name} {download_url} {md5sum}')
+
+cfg = configparser.ConfigParser()
+cfg.add_section('theia-download-plugins')
+cfg.set('theia-download-plugins', 'urls', '\n'.join(urls))
+
+with open('download-plugins.cfg', 'w') as f:
+  f.write(f"""\
+# This file is automatically generated from {__file__}
+# Do not edit directly.
+""")
+  cfg.write(f)