http: Break out the V1 Migration guide into a separate document
http: Break out the V1 Migration guide into a separate document

Problem
There is some confusion when people search the README and encounter sections in the "migration guide"
which are far from the header and aren't obviously about migration from previous functionality

Resolution
Break out the migration guide into a separate document

Result
It should be more obvious to what the document text is referring.

RB_ID=740238

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