Create sqlite db for dashboard

[binamkayastha]

Action Items:

• Save the sqlite DB as a artifact workflow similar to database.json, call it metrics.sqlite
• Make sure the workflow "retrieves" the metrics.sqlite from the previous run
• Have main.py create the sqlite file if it doesn't exist with the following create table statements

CREATE TABLE posts (
    id INTEGER PRIMARY KEY AUTOINCREMENT,
    pet_id TEXT NOT NULL,
    platform TEXT NOT NULL,
    post_id TEXT NOT NULL UNIQUE,
    post_url TEXT NOT NULL,
    posted_at TEXT NOT NULL,
    created_at TEXT NOT NULL DEFAULT (datetime('now')),
    updated_at TEXT NOT NULL DEFAULT (datetime('now'))
);

CREATE TABLE post_metrics (
    id INTEGER PRIMARY KEY AUTOINCREMENT,
    post_id TEXT NOT NULL,
    collected_at TEXT NOT NULL,
    likes INTEGER,
    reposts INTEGER,
    comments INTEGER,
    created_at TEXT NOT NULL DEFAULT (datetime('now')),
    updated_at TEXT NOT NULL DEFAULT (datetime('now')),
    FOREIGN KEY (post_id) REFERENCES posts (post_id)
);

We should branch off of https://github.com/codeforboston/CutePetsBoston/pull/155/changes because this change builds on it.

Right now collect_metrics on that branch updates database.json, but we want to change it to update the sqlite db instead