Implement retries (#56)

[Spiritreader]

Overview

This pull request implements the retry functionality mentioned in #21

It follows the outlined draft (#56) pretty closely, except for a bit more frontend fixes to display the correct color and strings when the service is pending (retrying)

Also for now, if a service enters the retry condition, hearbeats with that status do not count towards the uptime calculation.

This change requires a database migration for existing uptime kuma installations.

The new table looks like this:

CREATE TABLE "monitor" (
	"id"	INTEGER NOT NULL,
	"name"	VARCHAR(150),
	"active"	BOOLEAN NOT NULL DEFAULT 1,
	"user_id"	INTEGER,
	"interval"	INTEGER NOT NULL DEFAULT 20,
	"url"	TEXT,
	"type"	VARCHAR(20),
	"weight"	INTEGER DEFAULT 2000,
	"hostname"	VARCHAR(255),
	"port"	INTEGER,
	"created_date"	TIMESTAMP,
	"keyword"	VARCHAR(255),
	"maxretries"	INTEGER NOT NULL DEFAULT 0,
	PRIMARY KEY("id" AUTOINCREMENT),
	FOREIGN KEY("user_id") REFERENCES "user"("id") ON DELETE SET NULL ON UPDATE CASCADE
);

The monitor table received another field maxretries

The required migration script is NOT part of this PR, however the initial database has been updated accordingly.

Screenshot

[Saibamen]

@louislam: Do we have automatic DB migrations at server startup?

[louislam]

@louislam: Do we have automatic DB migrations at server startup?

Yes, I am implementing this.