This commit updates `ContentReader::read` to optionally close the
underlying `Reader` when a message is read that does not terminate
the DAP header immediately following the `Content-Length` header
field.
This fixes an infinite loop when parsing an invalid DAP message. In
particular, the infinite loop occurs when a cross-site HTTP request from
a browser running on the same host as a cppdap server is sent to the
server. As cross-site requests to the localhost can be triggered by
untrusted JavaScript, more validation of the DAP messages is required to
protect cppdap-based servers from malicious requests.
This commit introduces a new enum flag on both `Session` and
`ContentReader` to allow a user to indicate that the underlying `Reader`
should be closed when an invalid DAP message is received. The
server example has been updated to indicate that invalid messages
should result in closure of the underlying `Reader`.
e3379ed8c9