Support Verbose Errors and Logs

[charlespierce]

Info

• As part of improving errors, we want to support the --verbose flag to print additional error details.
• We also want to log those additional details, when we have them, regardless of the existence of the --verbose flag, so that users can access the more involved error details.

Changes

• Added an ErrorReporter type, responsible for composing the error message, additional details, and error log.
• Restructured the style module to only be responsible for the styling of the error messages, not the composition of various pieces.
• Updated the two binaries (main.rs and shim.rs) to use ErrorReporter for reporting any errors that are encountered.

Tested

• Added acceptance tests for the verbose flag and error logs.
• Manually tested that the verbose flag outputs as expected, and the error logs are written.

Notes

• The ErrorReporter is configured to treat the NOTION_DEV environment variable the same as the --verbose flag.
• Currently, when an error log is written, only the file name is outputted to the console, not the full path. All of the logs are written to NOTION_HOME/log/, so we will need to document that fact for users, or switch to outputting the entire path (could be long, especially on windows).
• The error log is only written if there is an underlying error, so that informational errors thrown directly from within Notion don't cause an unnecessary error log to be created.

Screenshots

Concise error with underlying cause

Verbose error with underlying cause

[dherman]

Looks like a nice approach! I made a few small style suggestions, which are up to you. There's one correctness issue but you can file a followup issue.