Add billing, payment, and signup links.

Dependencies

• [2] Z7FJX5KB Fix bad sample config.
• [3] H2ABVZI2 Add endpoint for payment request creation.
• [4] MJDIMD5B Improve documentation of local docker-compose setup.
• [5] 4B66XH43 Add sample billing config
• [6] M3KUPGZK Add invitation email template.
• [*] QO4NFWIY Added sample config file.

Change contents

• edit in conf/server/conf/aftok.cfg at line 31
  [4.12]→[2.4:27](∅→∅),[4.12]→[2.4:27](∅→∅)
  − networkMode = "test"