Add sandbox.env and update credential readme

clients/credential/README.md

@@ -25,7 +25,7 @@ which generates the `credential` binary in `target/debug/credential`.
 For example, you can get a credential worth 3 nym (3000000 unym) in a socks5 client that was already initialized like so:
 
 ```
-./target/debug/credential --config-env-file envs/sandbox.env --client-home-directory  ~/.nym/socks5-clients/cred_client  --nyxd-url  $SANDBOX_NYXD_VALIDATOR --mnemonic $MNEMONIC  --recovery-dir /tmp/recovery --amount 3000000
+./target/debug/credential --config-env-file envs/sandbox.env --client-home-directory  ~/.nym/socks5-clients/cred_client  --nyxd-url  https://sandbox-validator1.nymtech.net --mnemonic $MNEMONIC  --recovery-dir /tmp/recovery --amount 3000000
 ```
 
 More information regarding how to run the binary can be found by running it with the `--help` argument.

envs/sandbox.env

@@ -0,0 +1,24 @@
+CONFIGURED=true
+
+RUST_LOG=info
+RUST_BACKTRACE=1
+
+BECH32_PREFIX=nymt
+MIX_DENOM=unymt
+MIX_DENOM_DISPLAY=nymt
+STAKE_DENOM=unyxt
+STAKE_DENOM_DISPLAY=nyxt
+DENOMS_EXPONENT=6
+
+REWARDING_VALIDATOR_ADDRESS="nymt1mxuweurc066kprnngtm8zmvam7m2nw26yatpmv"
+MIXNET_CONTRACT_ADDRESS="nymt1dlsvvgey26ernlj0sq2afjluh3qd4ap0k9eerekfkw5algqrwqksaf2qf7"
+VESTING_CONTRACT_ADDRESS="nymt19g9xuqrvz2frv905v3fc7puryfypluhg383q9zwsmedrlqekfgys62ykm4"
+BANDWIDTH_CLAIM_CONTRACT_ADDRESS="nymt1rhmk9udessnv3r8f3eh2s03f45svnjaczpmcqz"
+MULTISIG_CONTRACT_ADDRESS="nymt142dkm8xe9f0ytyarp7ww4kvclva65705jphxsk9exn3nqdsm8jkqnp06ac"
+COCONUT_BANDWIDTH_CONTRACT_ADDRESS="nymt1ty0frysegskh6ndm3v96z5xdq66qzcu0aw7xcxlgp54jg0mjwlgqplc6v0"
+COCONUT_DKG_CONTRACT_ADDRESS="nymt1gwk6muhmzeuxje7df7rjvqwl2vex0kj4t2hwuzmyx5k62kfusu5qk4k5z4"
+GROUP_CONTRACT_ADDRESS="nymt14ry36mwauycz08v8ndcujghxz4hmua5epxcn0mamlr3suqe0l2qsqx5ya2"
+
+STATISTICS_SERVICE_DOMAIN_ADDRESS="http://0.0.0.0"
+NYXD="https://sandbox-validator1.nymtech.net"
+NYM_API="https://sandbox-validator1-api.nymtech.net/api"