Add TOML configuration file support

[Tatsh]

Overview

This adds support for reading configuration from a TOML file such as pyproject.toml to reduce clutter.

Layout is:

[tool.newrelic]
app_name = "app name"

Keys with . in them are expanded to be subkeys:

[tool.newrelic.browser_monitoring]
enabled = true

Anything that is a list in the layout is made into a string joined with a single space.

import-hook:... is translated as such and requires quotes in the keys:

[tool.newrelic.import-hook.module_name]
"sub.sub" = ["item1", "item2"]

error_collector.ignore_errors:

[tool.newrelic.error_collector]
ignore_errors = ["module.name:ClassName", "module.name:ClassName2"]

Environments use the tool.newrelic.env namespace:

[tool.newrelic.env.production]
app_name = "production name"

Expansion of the subkeys includes doing so in an environment section:

[tool.newrelic.env.production.transaction_tracer]
enabled = false

Related Github Issue

#1229

Testing

Tests have been added.

[CLAassistant]

All committers have signed the CLA.

[TimPansino]

Approving from my end, waiting on @hmstepanek to approve as well before merging.

[hmstepanek]

There are a couple more complicated settings that we have that I don't think are currently compatible with this parser. I went through our core config and looked for some others that are more complex like this. transaction_segment_terms is even more complex than the example below that I've noted and looks like:

    transaction_segment_terms = [
      {
        prefix = "WebTransaction/Custom",
        terms = ["one", "two", "three"]
      },
      {
        prefix = "WebTransaction/Uri",
        terms = ["seven", "eight", "nine"]
      }
    ]

[Tatsh]

transaction_segment_terms

That also appears to be one that is processed separately like url_rules and not taken from the configuration.

[TimPansino]

transaction_segment_terms

That also appears to be one that is processed separately like url_rules and not taken from the configuration.

Yes all 4 of these settings are not possible to configure with a config file.

_settings.url_rules = []
_settings.metric_name_rules = []
_settings.transaction_name_rules = []
_settings.transaction_segment_terms = []