Docassemble

Changed
- Tweaks to the `interview_url()` function.
Fixed
- Unicode error on interview page after interview decryption failure.
- Problem with list gathering and `.there_is_another`.

Fixed
- Problem with missing uid in background tasks.

Added
- The `DADateTime` class.
- The `time` and `datetime` `datatype`s for fields.
- The `format_datetime()` function.
- The `/api/session/back` API and the `go_back_in_session()` function.
- The `/api/privileges` and `/api/user/<user_id>/privileges` APIs, and
the `manage_privileges()` function.
- The `.as_serializable()` method of the `DAObject`.
Changed
- The `/api/session` POST API now returns the current question, unless the
`question` data value is set to `0`.
- The `/api/session` POST API now accepts file uploads.
- Changed the name "roles" to the name "privileges" in the
user-related APIs.
- The `set_user_info()` function can now be used to change user
privileges.
- Fields with `datatype: date` will now set a variable of type
`DADateTime`, rather than a plain text variable.
- The `today()` now returns a `DADateTime` object if it is called
without a `format` parameter.
- The JavaScript for the `show if` and `hide if` functionality now
animates the showing and hiding of fields.

Added
- Configuration directive `allow demo` for allowing demonstration
interviews in production mode.
- Ability to send e-mail using the Mailgun API instead of SMTP.
- The `decimal places` option for automatically formatting floating
point numbers passed to DOCX and PDF forms using `field code`,
`code`, or `field variables`.
Changed
- If the `checkin interval` configuration directive is set to `0`, the
browser will not "check in" at all.
- When the `/api/session/question` API encounters an undefined
variable for which a definition is not available, it will no longer
return an error code, but will return a success code and indicate
what variable was not defined.
Fixed
- Invalid HTML in navigation bar.
- Removed unnecessary invalidation of interview cache.
- Problem with address autocomplete when variable name contains a bracket.

Added
- The `get_chat_log()` function.
- An API interface.
- Administrative functions.
Fixed
- Result of `user_interviews()` was reporting the wrong `utc_modtime`.
- Error with `google maps api key` when an `api key` alone was set under
`google` in the Configuration.
- Problem with formatting of chat log after going back into a session.

Added
- The `send_fax()` function for sending faxes using Twilio.
- The `include_docx_template()` function for including .docx content
within a .docx file.