Add the second part of the multirack join service - #10989

control: job assigned to worker 01M0ED2CT5X9HGRCNE0K67PRJB [factory aws, i-07f1acafd05defa1f] (queued for 56 s)
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task: starting task 0: "setup"
task: process exited: duration 4089 ms, exit code 0
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task: starting task 1: "rust-toolchain"
task: process exited: duration 16075 ms, exit code 0
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task: starting task 2: "authentication"
task: process exited: duration 16 ms, exit code 0
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task: starting task 3: "clone repository"
task: process exited: duration 18936 ms, exit code 0
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task: starting task 4: "build"
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|  Documenting omicron-uuid-kinds v0.1.0 (/work/oxidecomputer/omicron/uuid-kinds)
|  Documenting dev-tools-common v0.1.0 (/work/oxidecomputer/omicron/dev-tools/common)
|     Finished `dev` profile [unoptimized + debuginfo] target(s) in 7m 26s
| warning: the following packages contain code that will be rejected by a future version of  [...]
| note: to see what the problems were, use the option `--future-incompat-report`, or run `ca [...]
|    Generated /work/oxidecomputer/omicron/target/doc/api_identity/index.html and 205 other  [...]
| 
| real     7:26.425446471
| user    20:13.499505105
| sys      4:18.225289997
| trap        0.302187519
| tflt        0.067460682
| dflt        0.059452092
| kflt        0.000039850
| lock  7:06:06.126586704
| slp   2:29:55.952002588
| lat        34.313182245
| stop     2:08.519614507
task: process exited: duration 832766 ms, exit code 0
|W| found 0 output files