WAITP-1479: Enable sending exports as an attachment to an email

[alexd-bes]

Issue WAITP-1479: Enable sending exports as an attachment to an email

Changes:

• Update constructExportEmail to generate an attachment when emailAsAttachment is true
• Update server-boilerplate Route to handle when response type is download but contents is not set
• Update export route to trigger a timeout and send attachments via email after 30 seconds

[rohan-bes]

Thanks for this @acdunham 🙏

Just a few comments around variable naming a code format, it took me a little bit of time to grasp exactly what was going on so that's why I made the suggestions.

But it's all looking good to pre-approving 👍

[rohan-bes]

Suggested change

	const { emailAsAttachment } = req.query;
	const { emailExportFileMode } = req.query;

Where emailExportFileMode: 'attachment' | 'downloadLink' (and defaulting to downloadLink). Feels a little clearer to me what this configuration does and what the options are

[rohan-bes]

Suggested change

	export const constructExportEmail = async (responseBody, req) => {
	const { emailAsAttachment } = req.query;
	const attachments = await generateAttachments(responseBody, emailAsAttachment);
	const message = constructMessage(responseBody, emailAsAttachment);
	return {
	subject: 'Your export from Tupaia',
	message,
	attachments,
	};
	export const constructExportEmail = async (responseBody, req) => {
	const { emailExportFileMode = 'downloadLink' } = req.query;
	const { error, filePath } = responseBody;
	const subject = 'Your export from Tupaia';
	if (error) {
	return {
	subject,
	message: `Unfortunately, your export failed.
	${error}`
	}
	}
	if (!filePath) {
	throw new Error('No filePath in export response body');
	}
	if (emailExportFileMode === 'attachment') {
	return {
	subject,
	message: 'Please find your requested export attached to this email.',
	attachments: await generateAttachments(filePath),
	}
	}
	const downloadLink = createDownloadLink(filePath);
	return {
	subject,
	message: `Please click this one-time link to download your requested export: ${downloadLink}
	Note that you need to be logged in to the admin panel for it to work, and after clicking it once, you won't be able to download the file again.`
	}

Decided to try re-writing this to flow a bit more clearly. What do you think? My preferences for this style were:

• Fewer instances of passing branching logic between functions (the emailExportFileMode logic now gets handled in one place)
• Not returning the attachments property when it's not needed feels a bit cleaner