Feature: add a new payment gateway that enables crypto and stock donations (The Giving Block integration)

[glaubersilva]

Resolves GIVE-3066

Description

This PR migrates our previous The Giving Block integration (built a few months ago but never released), made as an independent plugin to the GiveWP core, so now users can accept crypto and stock donations without the need to install additional plugins.

List of PRs merged to the epic branch:

1. Feature: add a new payment gateway sub-tab with 3 groups to manage The Giving Block settings #8202
2. Feature: add settings to enable connecting organizations through The Giving Block API #8204
3. Feature: add content to the "Get Started" tab with instructions about how to use the integration #8205
4. Feature: add shortcode and block to render TGB donation form #8208

Affects

Visuals

Testing Instructions

1. In your WP site, edit the wp-config.php file and set the connect server to use the sandbox mode, like this: define('GIVE_CONNECT_MODE', 'sandbox');
2. Go to the GiveWP > Settings > Payment Gateways > Crypto and Stock Donations page and connect an Organization (to make things easy in this step, just connect the GiveWP Sandbox organization using the following ID: 1189132016)
3. Go to a WP page and add the following shortcode there: [give_tgb_form type="iframe"] (you can change the type to "popup" as well), and make sure the Donation Form is displayed.
4. Delete the shortcode tested previously, and now add the new "The Giving Block by GiveWP" block to the page, and make sure the Donation Form is displayed.
5. Create test crypto donations following these steps: https://docs.thegivingblock.com/docs/how-to-make-a-test-crypto-donation
6. Create test stock donations following these steps: https://docs.thegivingblock.com/docs/how-to-make-a-test-stock-donation
7. Now disconnect the GiveWP organization, delete all plugin data in the Organization tab, start the onboarding of a new organization, and make sure the onboarding form works as expected.

IMPORTANT: is not possible make the onboarding with random data, it is necessary to use real organizations to make the onboarding form work, and we can find them in the http://candid.org/ website.

For more context, you can watch this demo video from the previous integration made as an independent plugin: https://www.loom.com/share/e4cfb95b7da4498197d9f5e45626765e

Pre-review Checklist

• Acceptance criteria satisfied and marked in related issue
• Relevant @unreleased tags included in DocBlocks
• Includes unit tests
• Reviewed by the designer (if follows a design)
• Self Review of code and UX completed

[glaubersilva]

Closing due to strategy change