Data migration: Finish baseurl conversion

[ChristopherChudzicki]

Finish the baseurl -> resource_link conversion started in #1002

Known remaining edge cases:

1. links with document fragments, e.g., [calendar]({{< baseurl >}}/pages/syllabus#Calendar)

2. links where the link text has square brackets or newlines (not double newlines—those aren't links according to Markdown).

3. links where the link casing is different from dirpath / filename casing, e.g., [Syllabus]({{< baseurl >}}/path/to/Syllabus) where the syllabus filename is syllabus not Syllabus.

4. Links where the title is an image, e.g.
   [![Boundary conditions animation.](/courses/civil-and-environmental-engineering/1-061-transport-processes-in-the-environment-fall-2008/lecture-notes/movie.jpg)]({{< baseurl >}}/resources/bounds3)

   ⚠️ Investigate the usage images in titles. Do we actually want to migrate/support this in future?

Related:

• Data migration: convert base_url shortcodes to resource_link shortcodes #969
• support links in resource short codes ocw-hugo-themes#523

[ChristopherChudzicki]

Even after #1013, the square bracket links BEFORE baseurl shortcodes are being escaped. See for example https://github.mit.edu/ocw-content-rc/18.04-fall-1999/commit/97032ead4f7bf3810c758522b30451dfc7538f00#diff-9674b1ed65559a66e97cbc6ada224051L24-R24

Consequences:

• this will break the baseurl link if they were working

BUT: Since we are working on replacing baseurl with resource_link anyway...one option is to not worry about this and just alter to replacement regex to catch both the escaped version (\[link title\]({{ baseurl}/...)) and unescaped version ([link title]({{ baseurl}/...))

[ChristopherChudzicki]

Closed in favor of Closing this in favor of #1233