RE: Conflict detection and logging in logical replication

Dear Hou,

Thanks for updating the patch! I think the patch is mostly good.
Here are minor comments.

0001:

01.
```
+<screen>
+LOG:  conflict detected on relation "schemaname.tablename": conflict=<literal>conflict_type</literal>
+DETAIL:  <literal>detailed explaination</literal>.
...
+</screen>
```

I don't think the label is correct. <screen> label should be used for the actual
example output, not for explaining the format. I checked several files like
amcheck.sgml and auto-exlain.sgml and func.sgml and they seemed to follow the
rule.

02.
```
+     <para>
+      The <literal>key</literal> section in the second sentence of the
...
```

I preferred that section name is quoted.

0002:

03.
```
-#include "replication/logicalrelation.h"
```

Just to confirm - this removal is not related with the feature but just the
improvement, right?


Best regards,
Hayato Kuroda
FUJITSU LIMITED