improve documentation and fix dht put bug

[Stebalien]

1. Document validators.
2. Pass DHT values as files as:
3. CLI arguments can't have nulls.
4. STDIN arguments can't have newlines.
5. IPNS records can have both

fixes #5112
fixes #6749

[Stebalien]

@alanshaw any objections to replacing ipfs dht put KEY STRING_VALUE with ipfs dht put KEY FILE? It allows us to actually put values with newlines and nulls.

[alanshaw]

Not at all, that would be better.

[pontiyaraja]

@Stebalien This changes is not yet tested by Circle CI, Please take a look at the build

https://circleci.com/gh/ipfs/go-ipfs/22265?utm_campaign=vcs-integration-link&utm_medium=referral&utm_source=github-build-link

Here is the test cases :

#!/bin/bash -eo pipefail go test -v ./... === RUN TestPublishDetailsWithKey --- SKIP: TestPublishDetailsWithKey (0.00s) ipns_test.go:13: === RUN TestPublishDetailsWithoutKey --- SKIP: TestPublishDetailsWithoutKey (0.00s) ipns_test.go:27: === RUN TestLogger --- PASS: TestLogger (0.31s) === RUN TestRequestBuilder --- PASS: TestRequestBuilder (0.00s) === RUN TestAdd --- PASS: TestAdd (0.06s) === RUN TestRedirect --- PASS: TestRedirect (0.00s) === RUN TestAddWithCat --- PASS: TestAddWithCat (0.02s) === RUN TestAddOnlyHash --- PASS: TestAddOnlyHash (1.23s) === RUN TestAddNoPin --- PASS: TestAddNoPin (0.02s) === RUN TestAddNoPinDeprecated --- PASS: TestAddNoPinDeprecated (0.03s) === RUN TestAddDir --- PASS: TestAddDir (0.00s) === RUN TestLocalShell --- PASS: TestLocalShell (0.00s) === RUN TestCat --- PASS: TestCat (0.00s) === RUN TestList --- PASS: TestList (0.00s) === RUN TestFileList --- PASS: TestFileList (0.00s) === RUN TestPins --- PASS: TestPins (0.07s) === RUN TestPatch_rmLink --- PASS: TestPatch_rmLink (0.03s) === RUN TestPatchLink --- PASS: TestPatchLink (141.01s) === RUN TestResolvePath --- PASS: TestResolvePath (0.00s) === RUN TestPubSub --- PASS: TestPubSub (0.02s) shell_test.go:282: subscribing... shell_test.go:286: sub: done shell_test.go:290: publishing... shell_test.go:292: pub: done shell_test.go:294: next()... shell_test.go:296: next: done. === RUN TestObjectStat --- PASS: TestObjectStat (0.00s) === RUN TestDagPut --- PASS: TestDagPut (0.05s) === RUN TestDagPutWithOpts --- PASS: TestDagPutWithOpts (0.04s) === RUN TestStatsBW --- PASS: TestStatsBW (0.00s) === RUN TestSwarmPeers --- PASS: TestSwarmPeers (0.00s) === RUN TestRefs --- PASS: TestRefs (0.00s) PASS ok github.com/ipfs/go-ipfs-api 142.905s ? github.com/ipfs/go-ipfs-api/options [no test files] ? github.com/ipfs/go-ipfs-api/tests [no test files]

[Stebalien]

This change is tested via the sharness test suite (test/sharness/t0170-dht.sh, "put round trips").