BUGFIX: PSQL Migration syntax fix

[gloriousCode]

PR Description

There was an issue migrating down using psql:

ERROR postgres.sql: failed to run SQL migration: failed to execute SQL query "ALTER TABLE withdrawal_history ALTER COLUMN exchange_name_id SET NULL;\n": pq: syntax error at or near "NULL"

Fixes a typo on migrations and also updates to use PSQL syntax

Type of change

• Bug fix (non-breaking change which fixes an issue)

How has this been tested

.\dbmigrate.exe -command=up
.\dbmigrate.exe -command=down
Until it worked

[codecov]

Codecov Report

Merging #550 into master will decrease coverage by 0.74%.
The diff coverage is 38.30%.

@@            Coverage Diff             @@
##           master     #550      +/-   ##
==========================================
- Coverage   45.68%   44.93%   -0.75%     
==========================================
  Files         234      246      +12     
  Lines       56464    59411    +2947     
==========================================
+ Hits        25797    26699     +902     
- Misses      27875    29666    +1791     
- Partials     2792     3046     +254     

Impacted Files	Coverage Δ
cmd/dbseed/candle.go	0.00% <0.00%> (ø)
cmd/dbseed/exchange.go	0.00% <0.00%> (ø)
cmd/dbseed/main.go	0.00% <0.00%> (ø)
config/config_types.go	0.00% <ø> (ø)
database/models/postgres/candle.go	0.00% <0.00%> (ø)
database/models/postgres/withdrawal_crypto.go	0.00% <ø> (ø)
database/models/postgres/withdrawal_fiat.go	0.00% <ø> (ø)
database/models/postgres/withdrawal_history.go	0.00% <0.00%> (-33.34%)	⬇️
database/models/sqlite3/withdrawal_crypto.go	53.66% <ø> (+0.99%)	⬆️
database/models/sqlite3/withdrawal_fiat.go	55.29% <ø> (ø)
... and 54 more

---

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[thrasher-]

tACK

On master:

ERROR postgres.sql: failed to run SQL migration: failed to execute SQL query "ALTER TABLE candle ALTER COLUMN aseet SET NULL;\n": pq: syntax error at or near "NULL"

PR:
Connected to: localhost 2020/09/09 14:01:20 OK 20200814113829_update_withdrawal_history_add_not_null_to_exchange_name_id\postgres.sql

[codelingo]

LGTM. 4 rules errored during the review.

[codelingo]

LGTM. 4 rules errored during the review.

[shazbert]

Tested Approved. Nice work!
Goosed it all the way down and all the way up, no issues.... no tissues needed.

[MadCozBadd]

tACKKKK