feat: add custom field default key

[MarcCon]

Adds a custom field for a default key in projects. If no key is selected, the key defined in the default key is fetched.

Closes #10

[barredterra]

On second though, the 'fetch from' brings the following problems:

• It always overrides a manually entered, different key.
• That could be solved by setting "fetch_if_empty": 1.
• However, that would still require that we always set a key, making the "no key" scenario impossible.

I think we'll need a more fine-tuned mechanism here, that could be described as "fetch only once". Only when setting/changing the project, the default key should be set, never otherwise. This could be achieved by extending this script to not only set the billable % but also the default key:

working_time/working_time/working_time/doctype/working_time/working_time.js

Lines 92 to 104 in ee26671

	project: function (frm, cdt, cdn) {
	// set billable time to 0% if Project is of Type "Internal", reset to 100% otherwise
	const child = locals[cdt][cdn];
	frappe.db
	.get_value("Project", child.project, "project_type")
	.then(({ message }) => {
	if (message && message.project_type == "Internal") {
	frappe.model.set_value(cdt, cdn, "billable", "0%");
	} else {
	frappe.model.set_value(cdt, cdn, "billable", "100%");
	}
	});
	},

[MarcCon]

If I have understood correctly the key is now fetched only once when the project is set. But you can also enter your own key and overwrite the default key.

[barredterra]

Mergifyio backport version-15

Manual backport: cf10a7a

[barredterra]

This change is unnecessary / doesn't do anything

[barredterra]

I've added this to ensure that the custom field is created when we install the update on existing sites.

[barredterra]

Added this condition to ensure we don't override existing data