Instead of lengthy blurbs, switch to single-line, machine-readable
standardized (https://spdx.dev) license identifiers. The Linux kernel
switched long ago, so there is strong precedent.
Three cases are handled: AGPL-only, Apache-only, and dual licensed.
For the latter case, I chose (AGPL-3.0-or-later and Apache-2.0),
reasoning that our changes are extensive enough to apply our license.
The changes we applied mechanically with a script, except to
licenses/README.md.
Closes#9937
The problem was that such a command:
```
alter table ks.cf with cdc={'ttl': 120};
```
would assume that "enabled" parameter is the default ("false") and,
in effect, disable CDC on that table. This commit forces the user
to specify that key.
Fixes#6475Closes#9720
Fixes#7128
CDC logs are not useful without at least delta_mode==keys, since
pre/post image data has no info on _what_ was actually done to
base table in source mutation.
Makes the "preimage" option for cdc non-binary, i.e. it can now
be "true"/"on", "false"/"off" or "full. The two former behaving like
previously, the latter obviously including all columns in pre image.
The goal is to have finer control over CDC "delta" rows, i.e.:
- disable them totally (mode `off`);
- record only PK+CK (mode `keys`);
- make them behave as usual (mode `full`, default).
This commit adds the necessary infrastructure to `cdc_options`.
