[Public] The link to the apply button appends the link to the site URL

**Describe the bug**
If the NGO adds a link to the application page without `https://` at the beginning of the URL, the link is embedded in the p4g site URL.
e.g.
> the link `ngohub.ro/ro/forms/contact`
> becomes `https://practice4good-staging.ngohub.ro/organizations/10/practice-program/ngohub.ro/ro/forms/contact`
> when trying to navigate there from `https://practice4good-staging.ngohub.ro/organizations/10/practice-program/3`

**To Reproduce**
Steps to reproduce the behavior:
1. Log in as an NGO in NGO Hub
2. If `Practice for Good` is not in your apps, add it by going to `All Apps > Practice for Good > Add`
3. Go to the `My apps` menu, on `Practice for Good` click `More`, then click on `Manage programs`
4. Add a new practice program with an application deadline in the future and with the "Link to the application page" a URL that doesn't contain "https://"
5. Go to the practice program and click "Apply"
6. The page doesn't take you to the link but to the `page-url/link`

**Expected behavior**
The link should take you to the `link` and shouldn't change it like this.

**Screenshots**