$Dollar symbol in PREFECT_API_DATABASE_CONNECTION_URL setting causes ValueError when resolving default_database_connection_url

[annshress]

First check

• I added a descriptive title to this issue.
• I used the GitHub search to find a similar issue and didn't find it.
• I searched the Prefect documentation for this issue.
• I checked that this issue is related to Prefect and not one of its dependencies.

Bug summary

When prefect's db connection url contains$ followed by non-alphabetic character, it raises ValueError. Because, it tries to use python's string.template.substitute which behaves like so.

Example DB connection url: postgresql+asyncpg://yoda:?0YpAwMy$&adQqcjSERqkqqc6BnS@some-domain.amazonaws.com:5432/prefect2

Reproduction

docker run -p 4200:4200 -it --rm prefecthq/prefect:2-python3.9

# Inside the container

export PREFECT_API_DATABASE_CONNECTION_URL="postgresql+asyncpg://yoda:?0YpAwMy$&adQqcjSERqkqqc6BnS@some-domain.amazonaws.com:5432/prefect2"
prefect server start

Error

Traceback (most recent call last):
  File "/usr/local/bin/prefect", line 5, in <module>
    from prefect.cli import app
  File "/usr/local/lib/python3.9/site-packages/prefect/__init__.py", line 86, in <module>
    prefect.logging.configuration.setup_logging()
  File "/usr/local/lib/python3.9/site-packages/prefect/logging/configuration.py", line 75, in setup_logging
    config = load_logging_config(
  File "/usr/local/lib/python3.9/site-packages/prefect/logging/configuration.py", line 40, in load_logging_config
    {
  File "/usr/local/lib/python3.9/site-packages/prefect/logging/configuration.py", line 43, in <dictcomp>
    if setting.value() is not None
  File "/usr/local/lib/python3.9/site-packages/prefect/settings.py", line 142, in value
    return self.value_from(get_current_settings(), bypass_callback=bypass_callback)
  File "/usr/local/lib/python3.9/site-packages/prefect/settings.py", line 154, in value_from
    value = settings.value_of(self, bypass_callback=bypass_callback)
  File "/usr/local/lib/python3.9/site-packages/prefect/settings.py", line 1372, in value_of
    value = setting.value_callback(self, value)
  File "/usr/local/lib/python3.9/site-packages/prefect/settings.py", line 418, in default_database_connection_url
    return templater(settings, value)
  File "/usr/local/lib/python3.9/site-packages/prefect/settings.py", line 316, in templater
    return original_type(template.substitute(template_values))
  File "/usr/local/lib/python3.9/string.py", line 121, in substitute
    return self.pattern.sub(convert, self.template)
  File "/usr/local/lib/python3.9/string.py", line 118, in convert
    self._invalid(mo)
  File "/usr/local/lib/python3.9/string.py", line 101, in _invalid
    raise ValueError('Invalid placeholder in string: line %d, col %d' %
ValueError: Invalid placeholder in string: line 1, col 35

Versions

Version:             2.13.4
API version:         0.8.4
Python version:      3.9.18
Git commit:          48d9d9a2
Built:               Fri, Sep 29, 2023 11:26 AM
OS/Arch:             linux/aarch64
Profile:             default
Server type:         ephemeral
Server:
  Database:          sqlite
  SQLite version:    3.40.1

Additional context

No response

[desertaxle]

Thanks for the issue @annshress! We'll look into resolving this, but in the meantime, you can escape the $ character by providing $$ in its place.

[ashrielbrian]

Is there a timeline for this to get fixed? This has cropped up a few times when using RDS to autogenerate and manage the master password, which occasionally generates a $ in the password string.

[desertaxle]

@ashrielbrian I have a fix in #14876 if you want to check it out!