Use HtmlString to distinguish between HTML and plain text strings

[jtojnar]

The database also contains other escaped values:

• https://github.com/fossar/selfoss/blob/ac61872689c24352ed912a231974376b15d41657/src/helpers/ViewHelper.php#L144
• https://github.com/fossar/selfoss/blob/0920dcbd1fe18a5369f7fe49dea8e7f0e2bfbeeb/src/controllers/Sources/Write.php#L78
• https://github.com/fossar/selfoss/blob/0920dcbd1fe18a5369f7fe49dea8e7f0e2bfbeeb/src/controllers/Sources/Write.php#L82

Similarly the view layer:

• https://github.com/fossar/selfoss/blob/ac61872689c24352ed912a231974376b15d41657/src/helpers/ViewHelper.php#L144

So I decided to first systematize the data model by using explicit object for HTML string.

Now we just need to remove the escaping everywhere else (will be a BC break).

[netlify[bot]]

✅ Deploy Preview for selfoss canceled.

Name	Link
🔨 Latest commit	b44d62f892c8b49d229d867547f022b7e9c05ed4
🔍 Latest deploy log	https://app.netlify.com/sites/selfoss/deploys/63ed478dd972010008392181