SearchLight complains when an AbstractModel has a field with no corresponding db column.

**Describe the bug**
Adding a field to an AbstractModel with no corresponding db column produces an error. I'm not sure if this is expected behaviour or not.

**Error stacktrace**
```
julia> all(Colour)
[ Info: 2022-01-18 08:42:01 SELECT "colours"."id" AS "colours_id", "colours"."name" AS "colours_name", "colours"."hex" AS "colours_hex", "colours"."other" AS "colours_other" FROM "colours" ORDER BY colours.id ASC
ERROR: SQLite.SQLiteException("no such column: colours.other")
Stacktrace:
[1] sqliteerror(handle::Ptr{Nothing})
@ SQLite ~/.julia/packages/SQLite/5DdLp/src/SQLite.jl:20
[2] sqliteerror(db::SQLite.DB)
@ SQLite ~/.julia/packages/SQLite/5DdLp/src/SQLite.jl:114
[3] macro expansion
@ ~/.julia/packages/SQLite/5DdLp/src/consts.jl:24 [inlined]
[4] sqliteprepare
@ ~/.julia/packages/SQLite/5DdLp/src/SQLite.jl:190 [inlined]
[5] SQLite._Stmt(db::SQLite.DB, sql::String)
@ SQLite ~/.julia/packages/SQLite/5DdLp/src/SQLite.jl:122
[6] Stmt
@ ~/.julia/packages/SQLite/5DdLp/src/SQLite.jl:152 [inlined]
[7] prepare
@ ~/.julia/packages/SQLite/5DdLp/src/tables.jl:104 [inlined]
[8] execute(conn::SQLite.DB, sql::String, params::NamedTuple{(), Tuple{}})
@ DBInterface ~/.julia/packages/DBInterface/1Gmxx/src/DBInterface.jl:130
[9] #execute#2
@ ~/.julia/packages/DBInterface/1Gmxx/src/DBInterface.jl:152 [inlined]
[10] execute
@ ~/.julia/packages/DBInterface/1Gmxx/src/DBInterface.jl:152 [inlined]
[11] query(sql::String, conn::SQLite.DB)
@ SearchLightSQLite ~/.julia/packages/SearchLightSQLite/cvPd7/src/SearchLightSQLite.jl:151
[12] query
@ ~/.julia/packages/SearchLightSQLite/cvPd7/src/SearchLightSQLite.jl:135 [inlined]
[13] DataFrame
@ ~/.julia/packages/SearchLight/B9d2o/src/SearchLight.jl:68 [inlined]
[14] find(m::Type{Colour}, q::SearchLight.SQLQuery, j::Nothing) (repeats 2 times)
@ SearchLight ~/.julia/packages/SearchLight/B9d2o/src/SearchLight.jl:85
[15] #all#36
@ ~/.julia/packages/SearchLight/B9d2o/src/SearchLight.jl:126 [inlined]
[16] all(m::Type{Colour})
@ SearchLight ~/.julia/packages/SearchLight/B9d2o/src/SearchLight.jl:126
[17] top-level scope
@ REPL[2]:1
```

**To reproduce**
Create a resource "colour":
```
module Colours

import SearchLight: AbstractModel, DbId
using SearchLight.Validation, ColoursValidator
import Base: @kwdef

export Colour

@kwdef mutable struct Colour <: AbstractModel
id::DbId = DbId()
name::String = ""
hex::String = ""
end

end
```
with a db migration:
```
module CreateTableColours

import SearchLight.Migrations: create_table, column, columns, primary_key, add_index, drop_table, add_indices

function up()
create_table(:colours) do
[
primary_key()
column(:name, :string)
column(:hex, :string)
]
end

add_index(:colours, :name)
end

function down()
drop_table(:colours)
end

end
```
This should work fine: you can create, save, update, etc. Colours.

Then edit Colours.jl:
```
@kwdef mutable struct Colour <: AbstractModel
id::DbId = DbId()
name::String = ""
hex::String = ""
other::String = ""
end
```

Then ```julia > all(Colour)``` or
```
julia > red = Colour(name = "red", hex = "FF0000", other = "foo")
Colour
| KEY | VALUE |
|----------------------|---------|
| hex::String | FF0000 |
| id::SearchLight.DbId | NULL |
| name::String | red |
| other::String | foo |

julia > save!(red)
```
throw the above error.

**Expected behavior**
The object "red" is saved to the db, ignoring the field "other".

**Additional context**
Please include the output of
`julia> versioninfo()`
and
`pkg> st`
Additional context
Please include the output of
julia> versioninfo()
and
pkg> st

```
julia> versioninfo()
Julia Version 1.6.2
Commit 1b93d53fc4 (2021-07-14 15:36 UTC)
Platform Info:
OS: Linux (x86_64-pc-linux-gnu)
CPU: Intel(R) Core(TM) i3-6100 CPU @ 3.70GHz
WORD_SIZE: 64
LIBM: libopenlibm
LLVM: libLLVM-11.0.1 (ORCJIT, skylake)
Environment:
JULIA_REVISE = auto
```
and
```
(Myproject) pkg> st
Project Myproject v0.1.0
Status `~/projects/Myproject/Project.toml`
[336ed68f] CSV v0.9.11
[c43c736e] Genie v4.9.0
[e115e502] GenieAuthentication v1.1.0
[6d011eab] Inflector v1.0.1
[e6f89c97] LoggingExtras v0.4.7
[739be429] MbedTLS v1.0.3
[0aa819cd] SQLite v1.3.0
[340e8cb6] SearchLight v2.0.1
[21a827c4] SearchLightSQLite v2.0.0
[4acbeb90] Stipple v0.19.3
[30ddb3f0] StippleCharts v0.16.0
[a3c5d34a] StippleUI v0.14.3
[ade2ca70] Dates
[56ddb016] Logging
```