Add the Content-Base hedaer to the default template

[StayPirate]

I figure out that this header is often used to highlight a direct link to the feed item by some MUA. Thunderbird is one of those.

A screenshot without the Content-Base header set:

A screenshot with the Content-Base header set:

N.B. Since I'm not a HTML expert, I'd like to hear some feedback about this change. Could this badly impact some emails? From its definition:

The Content-Base header provides a way for a server to specify a base URL for resolving URLs found in the entity body of a response.[5] The value of the Content-Base header is an absolute URL that can be used to resolve relative URLs found inside the entity.

I see this header might change how relative paths are resolved within the email's body.

[skx]

I don't see a problem with that change.

That said we already have code which is designed to convert relative links to absolute ones, which is here.

You might be describing a different thing - the behaviour of the mail client - but the actual content should already contain everything as absolute via the rewriting mentioned above.

Will look in more detail this evening, in the meantime thank-you for your contribution :)

[StayPirate]

That said we already have code which is designed to convert relative links to absolute ones, which is here.

You might be describing a different thing - the behaviour of the mail client - but the actual content should already contain everything as absolute via the rewriting mentioned above.

Right, I'm only talking about how MUAs render emails. According to your statement, I now think that this PR should not introduce any weird behavior.

Will look in more detail this evening, in the meantime thank-you for your contribution :)

My pleasure, I consider this project a little treasure 👍🏼. So, thank you.

[StayPirate]

The latter commit removes the item's link within the email body (text and html).

This probably needs to be taken with a grain of salt because if the MUA (email client) does not intentionally show the Content-Base header content (see screenshot above), then the user may end up with no easy way to click the link.

I found this useful since I use Thunderbird, which in turn reports the link as the Content-Base header. I leave this commit here for @skx to choose if he wants it or not.

[skx]

Yeah removing the links would be a mistake for the MUAs that don't show the content of the Content-Base header.

I'll merge the header-change in, but not the second commit.