Add new header_rewrite fields for topology-based DSes

[rawlinp]

What does this PR (Pull Request) do?

Add the new firstHeaderRewrite, innerHeaderRewrite, and lastHeaderRewrite fields to delivery services. These fields can only be used when the delivery service is assigned to a topology and are mutually exclusive with edgeHeaderRewrite and midHeaderRewrite, which can not be used if the delivery service is assigned to a topology.

NOTE: this PR intentionally does not create and link "location" parameters for these new header rewrite fields, because this extra information is unnecessary for client-side config generation via atstccfg and would just lead to a load of unnecessary complexity. Additionally, I think we should get rid of "location" parameters altogether, so increasing and perpetuating their usage is not ideal.

• This PR is not related to any Issue

Which Traffic Control components are affected by this PR?

• Traffic Ops

What is the best way to verify this PR?

Run the unit tests and TO API tests, verify they pass. Build the docs, verify nothing broke. View the rendered documentation changes, make sure they look correct.

The following criteria are ALL met by this PR

• This PR includes tests OR I have explained why tests are unnecessary
• This PR includes documentation OR I have explained why documentation is unnecessary
• This PR includes an update to CHANGELOG.md OR such an update is not necessary
• This PR includes any and all required license headers
• This PR ensures that database migration sequence is correct
• This PR DOES NOT FIX A SERIOUS SECURITY VULNERABILITY (see the Apache Software Foundation's security guidelines for details)

[ocket8888]

When you say that the new fields are "mutually exclusive" with the old ones, do you mean that only one set can be non-null/empty at a time (and presumably must be the topologies ones if it has an assigned topology and vice-versa), or just that only one set will have any effect at one time?

[rawlinp]

I believe this should answer that question: https://github.com/apache/trafficcontrol/pull/4807/files#diff-e35176dda777cf2b75d030e86b396b1aR486

[zrhoffman]

Docs build without warnings related to this PR, unit tests pass, API tests pass, delivery services work in CDN-in-a-Box as expected. Verified there are no regressions.