…on discovery

```
➜  sling-cli git:(feature/issue-45-expose-discover-conns) ✗ ./sling conns discover PROTON  -d2
sling - An Extract-Load tool | https://slingdata.io
Slings data from a data source to a data target.
Version dev

  Usage:
    sling [clean-partitions|conns|run]

  Subcommands:
    clean-partitions   Clean daily data for Timeplusd (Proton) tables
    conns              Manage and interact with local connections
    run                Execute a run

  Flags:
       --version   Displays the program version string.
    -h --help      Displays help with available flag, subcommand, and positional value parameters.

Expected a following arg for flag d2, but it did not exist.
➜  sling-cli git:(feature/issue-45-expose-discover-conns) ✗ ./sling conns discover PROTON
11:57PM WRN could not parse DEBUGINFOD_URLS: could not parse provided credentials / url
+---+----------+---------+-----------------+-------+
| # | DATABASE | SCHEMA  | NAME            | TYPE  |
+---+----------+---------+-----------------+-------+
| 1 | default  | default | test38_rd       | table |
| 2 | default  | default | test38_target1  | table |
| 3 | default  | default | v               | table |
| 4 | default  | default | mirror_v        | table |
| 5 | default  | default | mirror_v_sorted | table |
+---+----------+---------+-----------------+-------+
➜  sling-cli git:(feature/issue-45-expose-discover-conns) ✗ DEBUG=1 ./sling conns discover PROTON
11:58PM WRN could not parse DEBUGINFOD_URLS: could not parse provided credentials / url
11:58PM DBG opened "proton" connection (conn-proton-3WE)
11:58PM DBG database discover inputs: {"level":"table","pattern":"","schema":"","table":""}
11:58PM DBG unfiltered table records returned: 5
11:58PM DBG ["default.default.mirror_v","default.default.mirror_v_sorted","default.default.test38_rd","default.default.test38_target1","default.default.v"]
+---+----------+---------+-----------------+-------+
| # | DATABASE | SCHEMA  | NAME            | TYPE  |
+---+----------+---------+-----------------+-------+
| 1 | default  | default | test38_target1  | table |
| 2 | default  | default | v               | table |
| 3 | default  | default | mirror_v        | table |
| 4 | default  | default | mirror_v_sorted | table |
| 5 | default  | default | test38_rd       | table |
+---+----------+---------+-----------------+-------+
➜  sling-cli git:(feature/issue-45-expose-discover-conns) ✗
```