Substitute the layout %{content} token literally, not through String#%

[pcbeingused333]

Options#wrap inserted the email body into a layout with layout % {content: wrapped}. String#% treats every % in the layout string as a format directive, so a layout with a bare % blows up before the email is sent:

class OrderEmail < Courrier::Email
  layout html: "<table style='width:100%'><tr><td>\n%{content}\n</td></tr></table>"
end
# ArgumentError: malformed format string - %'

width: 100%, a percent-encoded URL, a line-height: 150% in an inline <style> — all of these are ordinary in an HTML email layout, and any one of them takes delivery down.

Fix

layout.gsub("%{content}") { wrapped }

%{content} is the only token the layout ever interpolated, so a literal substitution covers it. The block form of gsub (rather than gsub("%{content}", wrapped)) is deliberate: it passes the wrapped body through untouched when it contains \1, \\ or \&, which the string-replacement form would eat.

Behaviour change

A layout that wrote %% to get a literal % through String#% now keeps both characters. That escape was never documented (the README only shows %{content}), and it was the same feature that made bare % crash.

Tests

Options had no test file — the layout-wrapping path (Options#wrap) was only exercised indirectly. New test/courrier/email/options_test.rb covers the wrap, the literal %, and the backslash-sequence passthrough. With lib/courrier/email/options.rb reverted the % case errors exactly as above.

bundle exec rake test on Ruby 3.4: 162 runs, 306 assertions, 0 failures. rake standard clean.

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