bug(bigtable): Handle default values

[ron-gal]

No description provided.

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 16 lines in your changes missing coverage. Please review.

Project coverage is 44.86%. Comparing base (3eccded) to head (c6eb2b5).
Report is 98 commits behind head on main.

Files with missing lines	Patch %	Lines
...google/cloud/teleport/bigtable/BigtableToJson.java	0.00%	8 Missing ⚠️
.../teleport/bigtable/BigtableToVectorEmbeddings.java	0.00%	8 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##               main    #1940      +/-   ##
============================================
+ Coverage     42.83%   44.86%   +2.03%     
- Complexity     3424     3590     +166     
============================================
  Files           824      834      +10     
  Lines         48147    49617    +1470     
  Branches       5168     5227      +59     
============================================
+ Hits          20624    22261    +1637     
+ Misses        25847    25692     -155     
+ Partials       1676     1664      -12     

Components	Coverage Δ
spanner-templates	65.67% <ø> (+2.85%)	⬆️
spanner-import-export	63.80% <ø> (-0.10%)	⬇️
spanner-live-forward-migration	74.86% <ø> (-0.20%)	⬇️
spanner-live-reverse-replication	75.55% <ø> (+7.92%)	⬆️
spanner-bulk-migration	84.51% <ø> (+0.76%)	⬆️

Files with missing lines	Coverage Δ
...google/cloud/teleport/bigtable/BigtableToJson.java	61.95% <0.00%> (-0.69%)	⬇️
.../teleport/bigtable/BigtableToVectorEmbeddings.java	78.00% <0.00%> (-0.33%)	⬇️

... and 189 files with indirect coverage changes