## Issue Addressed
Fixes#1509
## Proposed Changes
Exit the beacon node if the eth1 endpoint points to an invalid eth1 network. Check the network id before every eth1 cache update and display an error log if the network id has changed to an invalid one.
## Issue Addressed
Resolve#1387
## Proposed Changes
Replace flag name **end_after_checks** to ** continue_after_checks**
Change condition to simple (remove **!**, It's no change logic.)
## Additional Info
Operation check
- [x] subcommand `eth1-sim` with ganach-cli
- [x] `./simulator eth1-sim` -> test is completes
- [x] `./simulator eth1-sim --continue_after_checks` -> test is never completes
- [x] `./simulator eth1-sim -c` -> test is never completes
- [x] `./simulator eth1-sim -c true` -> error: Found (clap)
- [x] `./simulator eth1-sim -c false` -> error: Found (clap)
- [x] subcommand `no-eth1-sim`
- [x] `./simulator no-eth1-sim` -> test is completes
- [x] `./simulator no-eth1-sim --continue_after_checks` -> test is never completes
- [x] `./simulator no-eth1-sim -c` -> test is never completes
- [x] `./simulator no-eth1-sim -c true` -> error: Found (clap)
- [x] `./simulator no-eth1-sim -c false` -> error: Found (clap)
## Issue Addressed
#1384
Only catch, as currently implemented, when dialing the multiaddr nodes, there is no way to ask the peer manager if they are already connected or dialing
## Issue Addressed
NA
## Proposed Changes
- Introduces the `valdiator_definitions.yml` file which serves as an explicit list of validators that should be run by the validator client.
- Removes `--strict` flag, split into `--strict-lockfiles` and `--disable-auto-discover`
- Adds a "Validator Management" page to the book.
- Adds the `common/account_utils` crate which contains some logic that was starting to duplicate across the codebase.
The new docs for this feature are the best description of it (apart from the code, I guess): 9cb87e93ce/book/src/validator-management.md
## API Changes
This change should be transparent for *most* existing users. If the `valdiator_definitions.yml` doesn't exist then it will be automatically generated using a method that will detect all the validators in their `validators_dir`.
Users will have issues if they are:
1. Using `--strict`.
1. Have keystores in their `~/.lighthouse/validators` directory that weren't being detected by the current keystore discovery method.
For users with (1), the VC will refuse to start because the `--strict` flag has been removed. They will be forced to review `--help` and choose an equivalent flag.
For users with (2), this seems fairly unlikely and since we're only in testnets there's no *real* value on the line here. I'm happy to take the risk, it would be a different case for mainnet.
## Additional Info
This PR adds functionality we will need for #1347.
## TODO
- [x] Reconsider flags
- [x] Move doc into a more reasonable chapter.
- [x] Check for compile warnings.
